The discovery of the circulation of the blood in animals was soon followed by conjectures concerning the existence of a like circulation in the sap of vegetables. These conjectures gave rise to the first improvements in vegetable physiology, which may be dated from the appearance of a set of queries concerning the motion of the juices of plants, published in the Philosophical Transactions, anno 1668. These queries immediately engaged Dr Beale and Dr Tonge, and afterwards Dr Grew, Mr Willoughby, Mr Ray, and Dr Lister, to enter upon the subject; who, in a great variety of observations, struck out the first considerable discoveries in the vegetable œconomy.

There is an atmospherical appearance which is not explained by the known laws of heat and cold. It is the breath of animals becoming visible, in being expired into an atmosphere which is cold or moist; and the transformation of transparent steam into the state of mist, when mixed with air which is of a colder temperature. Natural philosophers have certainly considered these appearances as being explained in the general law by which heat and cold are communicated among contiguous bodies, otherwise they would have endeavoured to point out this particular law, which seems to depart from a more general rule, or does not follow the natural course of things observed on other occasions. The subject of this paper is to investigate a certain rule which, in the case now mentioned, may be discovered as directing the action and effects of heat and cold; and to form a theory of rain upon that investigated rule, concerning the evaporation and condensation of water.

Though the labours of M. De Luc, and of the excellent observers who followed him, have brought the barometrical measurement of heights to very great exactness, they have not yet given to it the utmost perfection it can attain. Some causes of inaccuracy are still involved in it; of which we ought, at least, to estimate the effects, if we cannot correct them altogether. The allowance made on account of the temperature of the air, implies in it a hypothesis that has not been examined, nor even expressed, and many other circumstances that affect the denfity of the atmosphere, have either been wholly omitted, or improperly introduced. The object of the present paper is to correct, the errors that arise from these causes, or, where that cannot be done, to assign the limits within which those errors are contained.

By the introduction of letters into algebra, to denote all the quantities, both known and unknown, involved in an equation, this very important advantage was gained, that the final equation exhibited both a general rule for the solution of all similar problems, and also the limitations within which such problems were possible.

In the seventieth and seventy-first volumes of the London Philosophical Transactions, the reader will find an account of some Experiments and Observations made here upon cold in the years 1780 and 1781.

Though, at first, I had no other view but that of keeping a register of the very cold weather which set in on the 13th January 1780, yet I was soon led to extend the plan of my observations, upon meeting with a new phænomenon, which appeared to me to deserve some attention. This phænomenon consisted in a constant difference of temperature of the snow which, at that time, covered the fields, and that of the air at a few feet above: the snow being the coldest.

In an age like the present, when few things in nature feem to have eluded the researches of philosophy, when the communications of learning are as well established as those of commerce, it may appear somewhat surprising, that one of the most important productions of milk should still remain, in a great measure, unknown to the most enlightened parts of Europe.

Problem

Having the apparent distance of the Moon's centre from a fixed Star, or from the centre of the Sun, together with the apparent altitudes of their centres, to find the true distance.

Solution

The difference between the apparent and true altitudes, and the angles which the Moon and Star make with the zenith and each other, must be known before the several corrections of distance are computed.

I Did not return from the excursion on which I was when I had the pleasure to see you at Dundee till last Tuesday night. On my arrival, I found your letter respecting the phænomenon that lately happened in this neighbourhood. Although ill qualified to give you satisfaction upon this subject, I shall, however, comply with your desire, and give you the most accurate account of that phænomenon which I have been able to obtain.

In the register from which this abstract is taken, the numbers were marked every day at nine o'clock A. M. The quantity of rain was measured by means of a tin-cylinder, guarded by a wooden box, and sunk in the earth, into which the rain was received through a funnel, whereof the area was quadruple that of the cylinder. A gage, which floated on the surface of the water in the cylinder, had a rod fixed to it, divided into inches and tenths, which passed through the pipe of the funnel. The fourth part of the rise of this index marked the depth of rain which had fallen since the last observation, and these observations were generally made once in twenty-four hours.

When we trace the parts of which this terrestrial system is composed, and when we view the general connection of those several parts, the whole presents a machine of a peculiar construction by which it is adapted to a certain end. We perceive a fabric, erected in wisdom, to obtain a purpose worthy of the power that is apparent in the production of it.

The accuracy of modern observations has discovered irregularities in the motions of Jupiter and Saturn, which our knowledge of the laws of planetary gravitation has not as yet enabled us to explain. I have, therefore, long thought it probable that there may be planets without the orbit of Saturn, of sufficient magnitude to occasion these irregularities. This conjecture is confirmed by the discovery of a new planet.

This Abstract contains the medium heat for the half of each month, and is a continuation of that inserted in the last Volume of the Physical and Literary Essays.

Hawkhill is situated 1½ mile N. E. of Edinburgh.

The Observations of the Thermometer were made every day at 8 o'clock A. M.

The fall of the feudal system was accomplished, in the principal states of Europe, at a period when the revival of learning had diffused in society a spirit of reflection, and communicated, to the better sort, some knowledge of the history of the Greek and Roman republics. As it was, in general, the kings who conducted the attack on the privileges of the feudal nobility, the principal part of the spoils had fallen naturally to their share. But the people were warlike, the nobles were still; animated with the pride of rank, of family, and of their ancient consequence, and men, in general, had begun to speculate on their rights, and were unaccustomed to perceive, with satisfaction, the whole powers of government centred in the crown.

It cannot well be disputed, that, till the Greeks were possessed of the art of writing, they could have nothing that deserved the name of history. When that art was introduced among them is uncertain; but there is reason to believe, it was not known to them at the time of the Trojan war, as there is no mention of any writing in all the works of Homer; for the tablets, of which he speaks in one passage, did not contain any writing, but only marks or signs. At any rate, it cannot be supposed, that writing was much known or practifed, at that time, or indeed for long after. It appears from many charters, and other deeds, in this country, that men of the first families and fortunes in it could not, a few centuries ago, write their names; yet it is clear, from our having the use of coined money in commerce, and of cavalry in war, as well as from several other circumstances, that we were more civilized in those days than the Greeks could pretend to be when they first invaded Asia.

At a meeting of the Literary Class of the Royal Society, held on Monday 19th April 1784, the Reverend Dr Carlyle read an ode, written by the late Mr William Collins, and addressed to John Home, Esq; (author of Douglas, &c.) on his return to Scotland in 1749. The committee appointed to superintend the publication of the Society's Transactions, having judged this ode to be extremely deserving of a place in that collection, requested Mr Alex. Fraser Tytler, one of their number, to procure from Dr Carlyle every degree of information which he could give concerning it. This information, which forms a proper introduction to the poem itself, is contained in the two following letters.

H—, thou return'st from Thames, whose Naiads long

Have seen thee ling'ring, with a fond delay,

Mid those soft friends, whose hearts, some future day,

Shall melt, perhaps, to hear thy tragic song.

Go, not unmindful of that cordial youth,

Whom, long endear'd, thou leav'st by Lavant's side;

Together let us wish him lasting truth,

And joy untainted with his destin'd bride.

Go! nor regardless, while these numbers boast

My short-liv'd bliss, forget my focial name;

But think far off how, on the southern coast,

I met thy friendship with an equal flame!

Fresh to that soil thou turn'st, whose ev'ry vale

Shall prompt the poet, and his song demand:

To thee thy copious subjects ne'er shall fail;

Thou need'st but take the pencil to thy hand,

And paint what all believe who own thy genial land.

Few literary exertions put the author's abilities to a severer test than the composition of history. The poet may create a subject for himself, or he may adopt one that is but imperfectly known. In the composition of an epic poem, he instructs and pleases by exhibiting such a train of actions as might have taken place, and, unless he violates probability, his invention may bid defiance to restraint. If his work be imperfect, he has himself to blame, as those very powers which give the form to his subject, gave it first its existence.

In comparing ancient with modern historians, we meet with one remarkable circumstance in which they differ. The ancient historians are dramatic, the modern narrative. The ancients exhibit eminent persons delivering long speeches, adorned, as the occasion may require, with all the graces and force of eloquence. This is seldom done by the moderns. If it is ever necessary to give an account of what may have been delivered on an interesting subject by an eminent speaker, they tell us, excepting in such works as may be accounted translations, or in such histories, as those of Buchanan and Guicciardini, written manifestly after the models of antiquity, That he made use of such or such arguments; and, adhering strictly to the narrative form, they never venture on the bolder task of displaying him in his own person, delivering a long oration.

It is a maxim in physics, that “an effect ought not to be “ ascribed to the joint operation of many causes, if fewer “ are adequate to the production of it.” Frustra fit per plura, quod fieri potest per pauciora. This maxim is no less just when applied to language. It is equally unphilosophical in grammar and in physics, to multiply without necessity the principles from which the phænomena are to be explained.

It is reasonable to suppose, that the founders of the European states would, at least for some time after their conquests, retain much of their former political arrangements. The idea, therefore, which I have formed of their legislatures in their new situation may, in a great measure, be anticipated from the observations contained in the preceding part of this paper. At the same time, the change from the wilds of Germany to the cultivated provinces of the empire was very great: And it is necessary to survey, in general, the aspect which, on this event, the German governments might be expected to exhibit, in order, either to form an accurate conception of the general hypothesis I have adopted, or to perceive the propriety and application of those discussions which are intended for its support.