PHYSICS AND NATURAL HISTORY OF GENEVA. 263 
and rivers in the interior of southern Africa. , This cireumstance, however, loses 
its importance when we observe that, although referred to the same latitudes 
with those discovered by Livingstone and Burton, the names borne by these 
collections of water betray the error by which, while really belonging to equi- 
noctial Africa, they have been transported too far to the south. 
Before quitting our own planet to recall the communications relative to 
astronomy, I should occupy a moment with an account of some researches re- 
specting the atmosphere. ‘To Dr. Lombard we are indebted for a memoir treat- 
ing of the influence of altitude on rain. M. Gasparin, it will be remembered, 
claims to have established the law that the quantity of rain increases with the 
height. M. Lombard has collected, as bearing on this point, numerous obser- 
yations published in the United States, and, having compiled and compared 
many tables, arrives at results which, whether as regards the valley of the 
Mississippi or the whole country, entirely contradict the supposed law. M. de 
_la Rive, reminding us of a theory formerly advanced by himself regarding the 
formation of non-concentric hailstones, and ascribing it to the sudden congela- 
tion of collections of globules of water suspended in the atmosphere and cooled 
below zero, took occasion to announce to us that Professor Dufour, of Lau- 
sanne, has recently, by very ingenious experiments, furnished additional proba- 
bility to the theory, and shown the effect which violent concussion would have 
in producing the phenomenon. 
‘The principal discussions in regard to astronomy arose from the observa- 
tions of the total eclipse of the sun, July 18, 1860, made by Professor Plan- 
tamour, at Castellon de la Plana, in Spain, and by Colonel Gautier, near Tar- 
razona, It was certainly a fortunate circumstance for the Society that two of 
its own members were among the accomplished observers of these striking 
phenomena, and the details furnished by our colleagues were received with 
marked attention. As their memoirs have been published, I shall not here 
attempt a detailed analysis; I shall only observe that the essential point on 
which the discussions tarned was in relation to the red protuberances which, 
immediately after the disappearance of the sun, showed themselves on the edge 
of the obscure disk of the moon. Those observed by M. Gautier seem not to 
have been identical with those which M. Plantamour has so well described. 
The former particularly noticed one of these protuberances which, after having 
made its appearance at the commencement of the eclipse under the form of a 
small spot, continued to increase with a regular gradation and assumed the 
form of a large triangle, a little to the right of the zenith. But the chief sub- 
ject of variance between the two observers regards the cause of these protu- 
berances. If both agree in extolling the splendor of the spectacle, it is held, 
on the one hand, by M. Plantamour, to be a simple optical effect produced by 
the interposition of the screen which changes the direction of the sun’s rays ; 
while, on the other, M. Gautier thinks that the phenomenon is essentially solar. 
It would occupy us too long to state the arguments by which our learned ob- 
servers sustain the conclusions at which they arrived. I shall merely add, on 
the authority of M. Gautier, that the author of the annual report of the Astro- 
nomical Society of London seems to have adopted the opinion that the protu- 
berances pertain to the sun. 
M. Gautier has from time to time supplied us with information respecting 
the researches of M. R. Wolff on the spots on the sun. These researches 
confirm the existence of a period of about cleven years in the return of the 
spots, but their size is modified in an interval of five or six of those periods. 
The elder M. Wartmann stated, with regard to these spots, that when observed 
directly through the telescope they seem black, but when the image is received 
on a screen their appearance is red. He thinks that the phenomenon in the 
former case is an effect of contrast with the light of the orb. M. de la Rive 
