The comets which passed their perihelia in August, 1862, and January, 1866, will ever be memorable in the annals of science, as having led to the discovery of the intimate relationship between comets and meteors. These various bodies found revolving about the sun in very eccentric orbits may all be regarded as similar in their nature and origin, differing mainly in the accidents of magnitude and density. The recent researches, moreover, of Hoek, Leverrier and Schiaparelli, have led to the conclusion that such objects exist in great numbers in the interstellar spaces; that in consequence of the sun's progressive motion they are sometimes drawn towards the centre of our system; and that if undisturbed by any of the large planets they again pass off in parabolas or hyperbolas. When, however, as must sometimes be the case, they approach near Jupiter, Saturn, Uranus or Neptune, their orbits may be transformed into ellipses. Such, doubtless, has been the origin of the periodicity of the August and November meteors, as well as of numerous comets. In the present paper it is proposed to consider the probable consequences of the sun's motion through regions of space in which cosmical matter is widely diffused; to compare these theoretical deductions with the observed phenomena of comets, aerolites and falling stars; and thus, if possible, explain a variety of facts in regard to those bodies, which have hitherto received no satisfactory explanation.

The tendency of animals and plants to multiply beyond the means of subsistence and to spread over all available areas is well understood. What naturalists wish to know is not how species are dispersed, but how they are checked in their efforts to overrun the earth. Geographic barriers are rare, except in the case of oceans, and since even these were formerly bridged at the north, another cause must be sought. This has been found in the group of phenomena commonly hidden under the word climate, and nearly a century ago it was shown by Humboldt that temperature is the most important of these climatic factors.

In the northern hemisphere animals and plants are distributed in circumpolar belts or zones, the boundaries of which follow lines of equal temperature rather than parallels of latitude. They conform in a general way, therefore, with the elevation of the land, sweeping northward over the lowlands and southward over the mountains. Between the pole and the equator there are three primary belts – Boreal, Austral and Tropical – each of which may be subdivided into minor belts and areas. In the United States the Boreal and Austral regions have each been split into three secondary transcontinental zones. The Boreal are known as the Arctic, Hudsonian and Canadian; the Austral as the Transition, Upper Austral and Lower Austral. The subordinate faunas and floras need not be here considered.

Nobody had ever paid any correct attention to the fishes of this beautiful river, nor indeed of the whole immense basin, which empties its water into the Mississippi, and hardly twelve species of them had ever been properly named and described, when in 1818 and 1819, I undertook the labour of collecting, observing, describing, and delineating those of the Ohio. I succeeded the first year in ascertaining nearly eighty species among them, and this year I added about twenty more, making altogether about one hundred species of fish, whereof nine tenths are new and undescribed.

Many of them have compelled me to establish new genera, since they could not properly be united with any former genus; and I could have increased their number, had I been inclined, as will be seen in the course of this ichthyology; but I have in many instances proposed sub-genera and sections instead of new genera. I sent last spring to Mr. Blainville of Paris, a short account of some of them, to be published in his Journal of Natural History, in a Tract named Prodromus of seventy new genera of Animals and fifty new genera of Plants from North America, and I now propose to publish a complete account of all the species I have discovered.

It seems to me that there is much confusion of ideas in the general statement of the variability of species so often repeated lately. If species do not exist at all, as the supporters of the transmutation theory maintain, how can they vary, and if individuals alone exist, how can the differences which may be observed among them prove the variability of species? The fact seems to me to be that while species are based upon definite relations among individuals which differ in various ways among themselves, each individual, as a distinct being, has a definite course to run from the time of its first formation to the end of its existence, during which it never loses its identity nor changes its individuality, nor its relations to other individuals belonging to the same species, but preserves the categories of relationship which constitute specific or generic or family affinity, or any other kind or degree of affinity. To prove that species vary it should be proved that individuals born from common ancestors change the different categories of relationship which they bore primitively to one another. While all that has thus far been shown is, that there exists a considerable difference among individuals of one and the same species.

The earliest geological induction of primeval man is the doctrine of terrestrial catastrophe. This ancient belief has its roots in the actual experience of man, who himself has been witness of certain terrible and destructive exhibitions of sudden, unusual telluric energy. Here in America our own species has seen the vast, massive eruptions of Pliocene basalt, the destructive invasion of northern lands by the slow-marching ice of the glacial period, has struggled with the hardly conceivable floods which marked the recession of the frozen age, has felt the solid earth shudder beneath its feet and the very continent change its configuration. Yet these phenomena are no longer repeated; nothing comparable with them ever now breaks the geological calm.

When complete evidence of the antiquity of man in California and the catastrophes he has survived come to be generally understood, there will cease to be any wonder that a theory of the destructive in nature is an early, deeply rooted archaic belief, most powerful in its effect on the imagination. Catastrophe, speaking historically, is both an awful memory of mankind and a very early piece of pure scientific induction. After it came to be woven into the Sanskrit, Hebrew, and Mohammedan cosmogonies, its perpetuation was a matter of course.

From the believers in catastrophe there is, however, a totally different class of minds, whose dominant characteristic is a positive refusal to look further than the present, or to conceive conditions which their senses have never reported.

Diversity and Differentiation

In 1876 Simon Newcomb (an American polymath who published in mathematics, astronomy, physics, and economics) wrote an essay, “Abstract Science in America, 1776–1876,” for an issue of the North American Review dedicated to the centennial of the American Revolution. The essay provides a recap of American science – clear, concise, contemporary – and a view of what contemporaries thought about the state of American science:

Three themes dominated the science of this period: exploration, classification, and utilization. Jefferson, in his famous letter of instruction to Meriwether Lewis, illustrated the tone: “The object of your mission is to explore the Missouri river, & such principal stream of it, as, by it's course & communication with the waters of the Pacific Ocean, whether the Columbia, Oregon, Colorado or any other river, may offer the most direct and practicable water communication across this continent, for the purposes of commerce.” He also listed among the “objects worthy of notice” animals, plants, minerals, soil, topography, and climate. Embedded in this letter – the main focus of which was trade, commerce, and navigation – were Jefferson's own scientific interests, kept subordinate because of the reluctance of Jefferson's largely mercantile oriented congress to pay for science that did not promise a commercial payoff. The pro-British mercantile elite found many of the enlightenment tendencies of the Francophile Jefferson suspect, superfluous, ungodly, but this judgment was more a matter of politics, balance, economy, and utility than any true anti-science bias. The outstanding American scientists of the previous century, Franklin, Bartram, Rittenhouse, all had roots in the mercantile class and were themselves mindful of the young country's need for practical and useful knowledge. Jefferson too thought of science in terms of utility, for though he might not view commerce as the sole guide for scientific activity, he always tended toward a measure of utility.

This anthology of nineteenth-century American science writing began with my pursuit of American studies. Over the years I became intrigued by the scientists of the period, especially the first half of the century. They often wrote about science and natural history, literature and exploration. When I queried my science friends on their familiarity with scientists of the nineteenth century, they recognized names, knew who represented their own fields, but had rarely read any of the original work. I soon realized one of the reasons why when I tried to find ready sources for the primary works of the early naturalists (Say, Nuttall, Wilson). Not only were there no anthologies of early American science, but even the compendiums of nineteenth-century science writing, of which there are scores, rarely bothered with the Americans. If by chance they should, the same three or four names appeared: Joseph Henry, Oliver Wendell Holmes Sr., a smattering of William James as philosophy of science or Thoreau as natural history. I came away from these anthologies with the uncomfortable feeling that American science in the nineteenth century was inferior at best, non-existent at worst. Of course, there might be good reason for this omission from the British and European point of view; simply put, they were far ahead of the Americans in both productivity and scientific infrastructure, but that did not mean science in the United States had not made contributions to the century or that it would not be of interest to students of the American nineteenth century.

A current is a progressive motion of the water, causing all floating bodies to move that way towards which the stream is directed. The set of a current is that point of the compass towards which the waters run, and its drift is the rate it runs per hour. The most usual way of discovering the set and drift of an unknown current, is the following, supposing the current at the surface to be much more powerful than at a great distance below the surface:—

Take a boat a short distance from the ship, and, by a rope fastened to the boat's stern, lower down a heavy iron pot or loaded kettle to the depth of 80 or 100 fathoms; then heave the log, and the number of knots run out in half a minute will be the miles the current sets per hour, and the bearing of the log will show the set of it.

There is a very remarkable current, called the Gulf Stream, which sets in a north-east direction along the coast of America, from Cape Florida towards the Isle of Sables, at unequal distances from the land, being about 75 miles from the short of the southern States, but more distant from the shore of the northern States. The width of the stream is about 40 or 50 miles, widening towards the north.

On the Laws of Evolution

Wallace and Darwin have propounded as the cause of modification in descent their law of natural selection. This law has been epitomized by Spencer as the “preservation of the fittest.” This neat expression no doubt covers the case, but it leaves the origin of the fittest entirely untouched. Darwin assumes a “tendency to variation” in nature, and it is plainly necessary to do this in order that materials for the exercise of a selection should exist. Darwin and Wallace's law is, then, only restrictive, directive, conservative, or destructive of something already created. Let us, then, seek for the originative laws by which these subjects are furnished – in other words, for the causes of the origin of the fittest.

The origin of new structures which distinguish one generation from those which have preceded it, I have stated to take place under the law of acceleration. As growth (creation) of parts usually ceases with maturity, it is entirely plain that the process of acceleration is limited to the period of infancy and youth in all animals. It is also plain that the question of growth is one of nutrition, or of the construction of organs and tissues out of protoplasm.

The construction of the animal types is restricted to two kinds of increase – the addition of identical segments and the addition of identical cells. The first is probably to be referred to the last, but the laws which give rise to it cannot be here explained.

In the Journal of Lewis and Clark, there is an account of a quadruped which appears to have not excited that attention which it merits. The following extracts are made from the above mentioned work: “Saw the skin of a mountain sheep, which the Indians say lives among the rocks in the mountains: the skin was covered with white hair, the wool long, thick and coarse, with long coarse hair on the top of the neck and the back, resembling somewhat the bristles of a goat.” Vol. II. p. 49.

“The sheep is found in many places, but mostly in the timbered parts of the rocky mountains. They live in greater numbers on the chain of mountains forming the commencement of the woody country on the coast, and passing the Columbia between the falls and rapids.” Vol. II. p. 169.

The latter passage was written while our travelers wintered at the mouth of the Columbia river. But on their return, at Brant Island, an Indian “offered two sheep skins for sale: one, which was the skin of a full-grown sheep, was as large as that of a common deer; the second was smaller, and the head part, with the horns remaining, was made into a cap, and highly prized as an ornament by the owner. The Clahelellahs informed us that the sheep was very abundant on the heights, and among the cliffs, of the adjacent mountains; and that these two had been lately killed out of a herd of thirty-six, at no great distance from the village.” Vol. II. p. 233.

The surface of the earth being partly formed by water and partly by land, and the organization of all living beings standing in close relation to the one or the other of these mediums, it is in the nature of things that no single species, either of animals or plants, should be uniformly distributed over the whole globe. Yet there are some types of the animal as well as of the vegetable kingdom which are equably distributed over the whole surface of the land, and others which are as widely scattered in the sea, while others are limited to some continent or some ocean, to some particular province, to some lake, nay, to some very limited spot of the earth' surface.

As far as the primary divisions of animals are concerned, and the nature of the medium to which they are adapted does not interfere, representatives of the four great branches of the animal kingdom are everywhere found together. Radiata, Mollusks, Articulata, and Vertebrata occur together in every part of the ocean, in the Arctics, as well as under the equator, and near the southern pole as far as man has penetrated; every bay, every inlet, every shoal is haunted by them. So universal is this association, not only at present but in all past geological ages, that I consider it as a sufficient reason to expect that fishes will be found in those few fossiliferous beds of the Silurian System in which thus far they have not yet been found.

Although the discoveries of Oersted, Arago, Faraday, and others, have placed the intimate connection of electricity and magnetism in a most striking point of view, and although the theory of Ampere has referred all the phenomena of both these departments of science to the same general laws, yet until lately one thing remained to be proved by experiment, in order more fully to establish their identity; namely, the possibility of producing electrical effects from magnetism. It is well known that surprising magnetic results can readily be obtained from electricity, and at first sight it might be supposed that electrical effects could with equal facility be produced from magnetism; but such has not been found to be the case, for although the experiment has often been attempted it has nearly as often failed.

It early occurred to me, that if galvanic magnets, on my plan, were substituted for ordinary magnets, in researches of this kind, more success might be expected. Besides their great power, these magnets possess other properties, which render them important instruments in the hands of the experimenter; their polarity can be instantaneously reversed, and their magnetism suddenly destroyed or called into full action, according as the occasion may require. With this view, I commenced, last August, the construction of a much larger galvanic magnet than, to my knowledge, had before been attempted, and also made preparations for a series of experiments with it on a large scale, in reference to the production of electricity from magnetism.

1. THE Erythronium albidum of Nuttall is a common plant near Lexington, where it is called Lambs-tongue. The root or bulb is used against the Scrophula [sic], being stewed with milk or cream, and applied to the scrophulous [sic] sores, which it will cure. The yellow flowered species or Erythronium luteum, has probably the same property. – Communicated by Mr. Crockett, a medical student.

2. The Bear-grass is not a grass; but a fine rare plant peculiar to the western states, the Helonias angustifolia of Michaux, which I have ascertained to be different from Helonias and called Cyanotris pratensis. Its bulb or root is employed in Kentucky and near Lexington for the cure of the Inflamed Breast: it is mashed and applied to the part as a poultice – Communicated by Mr. Crockett.

3. The Helenium autumnale is called Sneezeweed in Kentucky, owing to its strong sternutory [sic] properties. If the flowers are dried and snuffed, they will occasion a strong fit of sneezing.

4. The root and leaves of the Evonymus atropurpureus, which are called Arrow-wood or Wahoon in Kentucky, are used with efficiency in the Influenza, Cough, Colds &c. in the shape of tea or decoction.

5. Dr. Samuel Brown having procured and shown me the plant which is said to occasion in Kentucky the Milk Fever, I have ascertained that it is the Euphorbia peploides (E. peplus of Pursh, not Lenneus) which is not uncommon on the cliffs and rocky situations in Kentucky. When eaten by cows through chance, it gives them a fever, and their milk becomes poisonous, producing the milk fever in those who drink it.

6. Many plants are called Gentian in Kentucky and used as succedanea of the foreign Gentian; they are Triosteum major and Tr. minor, Sabatia angularis, Gentiana amarelloides, and several other species of this last genus.

7. The root of the large Plantain, Plantago major, has lately been recommended in Europe as a good febrifuge.

8. The Water Horehound, or Lycopus virginicas, has lately been discovered to be an excellent remedy in Hemoptysis or spitting of blood. It is used in decoction or tea-like.

I have been lately requested to determine the distribution of energy in the spectrum of an argand burner, and have been able to do this by means of the apparatus and methods previously employed at the Allegheny observatory for mapping the invisible spectrum of the sun. The results are curious; and, in the hope that they may also be found useful, I desire to communicate them to the academy. The difficulty is such a determination lies in the mapping of something which is wholly invisible; and it has not been made before, I presume, in spite of its economical importance, because there has been no means known of measuring this invisible energy, except in a rough way, by the thermometer or themopile, by a process which gives incomplete results.

It was my object not merely to indicate how much of the radiation from a gas-burner was visible, and how much was not, but to give a map of its distribution on the normal or wave-length scale, which would enable any one to see the quality and amount of the energy in each part of the light and head region.

The ordinary argand burner, burning common house-gas within a glass chimney, was first placed at the centre of the curvature of a large Rowland concave grating; and, but means of the bolometer, the head was measured at successive points in the spectrum down to a wave-length of about.001 mm., where the overlapping second spectrum began to be sensible.

The recent excellent works by Dujardin,1 Diesing,2 and Robin,3 upon animals and vegetable parasites of living animals, render another systematic record of the labors in this field almost superfluous; and the object of the present memoir is simply to give the result of a series of observations, commenced several years ago, upon associated entozoan and entophyta, constituting a flora and fauna within animals.

The existence of entozoan, or of animals living within other species has, from the most remote times, attracted attention, on account of the peculiarity of their position, the unpleasant ideas associated with them, the sufferings they frequently induce, and the difficulty of explaining their mode or origin.

The entozoan have always constituted the strongest support of the doctrine of equivocal or spontaneous generation, one which has found distinguished disciples even to the present time; but since the days when barnacles were supposed to originate from the foam of the ocean, and ducks and geese to be developed from barnacles, this belief has been so weakened by the accumulation of facts, undenied and undeniable by the supporters of the doctrine, that it bids fair soon to be little more than an echo of the past.

The entozoan have always constituted the strongest support of the doctrine of equivocal or spontaneous generation, one which has found distinguished disciples even to the present time; but since the days when barnacles were supposed to originate from the foam of the ocean, and ducks and geese to be developed from barnacles, this belief has been so weakened by the accumulation of facts, undenied and undeniable by the supporters of the doctrine, that it bids fair soon to be little more than an echo of the past.

The origin of the existing distribution of species in this department of zoology deserves attentive consideration. Two great causes are admitted by all, and the important question is, how far the influence of each has extended. The first is, original local creations; the second, migration.

Under the first head, we may refer much that we have already said on the influence of temperature, and the restriction of species to particular temperature regions. It is not doubted that the species have been created in regions for which they are especially fitted; that their fitness for these regions involves an adaptation of structure thereto, and upon this adaptation, their characteristics as species depend. These characteristics are of no climatal origin. They are the impress of the Creator's hand, when the species had their first existence in those regions calculated to respond to their necessities.

The following questions come under this general head:—

1. Have there been local centres of creation, from which groups of species have gone forth by migration?

2. Have genera only and not species, or have species, been repeated by creation in distinct and distant regions?

3. How closely may we recognize in climatal and other physical conditions, the predisposing cause of the existence of specific genera or species?

With regard to the second head, migration, we should remember, that Crustacea are almost wholly maritime or marine; that marine waters are continuous the globe around; and that no sea-shore species in zoology are better fitted than crabs for migration.

The screw is the simplest instrument for converting a uniform motion of rotation into a uniform motion of translation (see “Mechanics,” vol. xv, p. 754). Metal screws requiring no special accuracy are generally cut by taps and dies. A tap is a cylindrical piece of steel having a screw on its exterior with sharp cutting edges; by forcing this with a revolving motion into a hole of the proper size, a screw is cut on its interior forming what is known as a nut or female screw. The die is a nut with sharp cutting edges used to screw upon the outside of round pieces of metal and thus produce male screws. More accurate screws are cut in a lathe by causing the carriage carrying the tool to move uniformly forward, thus a continuous spiral line is cut on the uniformly revolving cylinder fixed between the lathe centres. The cutting tool may be an ordinary form of lathe tool or a revolving saw-like disk (see “Machine Tools,” vol. xv, p. 153).

Errors of Screws. – For scientific purposes the screw must be so regular that it moves forward in its nut exactly the same distance for each given angular rotation around its axis. As the mountings of a screw introduce many errors, the final and exact test of its accuracy can only be made when it is finished and set up for use.