300 SOCIETY OF PHYSICS AND NATURAL HISTORY OF GENEVA. 



remarks with wliicli he accompauied the readiug of the memoirs at the 

 sessions iu whicli we had the pleasure of meeting him. 



At the mention of Professor James David Forbes we find ourselves 

 in some sort at home, since, besides not a few investigations in pure 

 phj\sics, a great part of the researches of this learned Scotchman had 

 for their object our mighty Alps, with the glaciers which cover their 

 summits and descend into their valleys. It was from no su])erficial 

 inspection that Forbes described the geology of these mountains and 

 the movement of the glaciers ; like de JSaussure, upon whose labors he 

 seems to have modeled his own, he has given us his Travels in the Alps, 

 founded upon very numerous excursions, as stated by himself in a pre- 

 face written in 1843: "It was my privilege to receive, iu earliest youth, 

 the most vivid impressions from the contemplation of mountain scenery, 

 and 1 have renewed those impressions in after-life, by traversing the 

 chain of the Alps twenty-seven times by twenty-three different passes, 

 and exploring all the lateral valleys of the great central group of 

 Europe." It was through these multiplied excursions, which were 

 repeated nearly every year since ISlo, that Forbes was enabled to 

 deduce his theory of the movement of glaciers, which he compares to 

 a river descending slowly into the valley. But his explorations were 

 Bot limited to the Alps; they were extended to the volcanic regions, 

 both ancient and recent, of the Gulf of Naples and of Ardeche, as well 

 as to the glaciers and fiords of Norway. Unhappily, the first germs of 

 consumption were developed in his system during these last-mentioned 

 excursions ; and it was this disease which conducted him to the tomb, 

 December 31, ISGS, at the age of fifty-nine years, after long sufferings, 

 partially alleviated by intervals of comparative good health. 



Professor Forbes was a member of our society from the year 1833. 

 He was often present at our sittings, giving us the earliest fruits of the 

 observations which he had just made in the neighboring Alps and com- 

 municating them to the i)ublic through the medium of the Bibliotheque 

 TJniverseUe, as well as the scientific collections of his native country. 

 Some idea of the great intellectual activity of one who died when still in 

 the flower of his age may be formed from the fact that his biographer, 

 M. Eeikie, has recorded the titles of one hundred and forty-two works 

 or memoirs Avhich he had published ; of these I shall cite but one as 

 specially interesting us, namely, a biographic notice of our colleague, 

 Professor Necker. 



After these biographical and administrative details let us pass to the 

 liroper labors of our society, and commence with the i)hysical and math- 

 ematical sciences. 



§ 1. — Astronomy. 



Professor Gautier has continued to make the society acquainted with 

 the i)rogress of astronomy, and particularly with that remarkable class 

 of recent investigations to which the employment of the spectral method 

 has given rise. The observations of the eclipse of the 18th of August, 

 1868, as well as the study of the constitution of the sun, and other ce- 

 lestial bodies, have formed the subject of the greater part of his com- 

 munications. M. Soret has also occupied our attention with the chem- 

 ical composition of the solar atmosphere, the exterior strata of which 

 seem to contain only hydrogen and not a multiplicity of gases or vapors, 

 a fact which has been brought forward by certain persons as an objec- 

 tion to the theory by which M. Kirchoff has explained the black stripes 



