Those who have taken part in the recent discussions as to the origin of lake-basins are well aware that one of the chief causes which has retarded a settlement of the controversy is the ignorance prevailing as to the true form of such basins. Even as to the Swiss and Lombard lakes, constantly visited as they have been by men of science, the data are extremely scanty and no way reliable. A few soundings made by myself in the Lake of Como, in 1863, and referred to in a paper published in the Philosophical Magazine in the following December, increased my conviction of the importance of instituting careful and exact measurements of the form and dimensions of the beds of lakes, if we were to reason securely as to their origin. I expressed that conviction at the time to an active local naturalist, Don Baldassare Bernasconi, residing at Laglio. In 1865 Signer Gentilli, one of the engineers of the Lombardo-Venetian Railway, being for some months on the Lake, proposed to undertake a regular survey of the bed of the Lake by means of a complete series of soundings, and devised an instrument for measuring the distances traversed horizontally in a boat, corresponding to each cast of the sounding line. Signer Gentilli found two active coadjutors in the persons of the above-named ecclesiastic, and of Dr. Guiseppe Casella, also resident at Laglio, on the Lake.