262 PROCEEDINGS OF THE SOCIETY OF 
of the earth. M. Ritter informs us that the manner in vvhich these experiments 
have been conducted, and the possibility that unknown and unconsidered sub- 
stances may exist in the mountain, on the two sides of which the experiments 
were made, do not authorize us to accord to the results obtained the same con- 
fidence which should be inspired by experiments of the nature of those of 
Cavendish. Again, the operations in England, conducted by the commission 
for restoring the standard of measures of length, (the yard,) have found in M. 
Ritter a reporter qualified to convey to his colleagues a clear idea of the diffi- 
culties encountered, and of the scrupulous precautions taken to obtain a solu- 
tion of the problem. . 
The study of the periphery of our globe, and the phenomena it presents, have 
been the subject of several communications. M. Chaix, in giving a summary 
account of the voyage of McClintock to the polar regions, showed that the 
boreal lands have in general a higher relief than was heretofore supposed. The 
mean relief of the islands discovered since the voyages of Captain Koss reaches - 
2,000 feet. Different indications lead to the belief in recent upheavals. To 
the same colleague we are indebted for a sketch of a memoir by Colonel Gra- 
ham, on the semi-diurnal tides of Lake Michigan, from which it results that the 
high spring tide at the syzygies rises to 3.48 inches, and M. Graham thinks 
would reach 4 inches, were all causes of disturbance removed. 
Professor Wartmann and M. de Saussure on two occasions occupied the 
attention of the Society with a work by M. Thomassé, on the hydrology of the 
southern part of the United States. This latter savant, accepting the state- 
ment of American engineers that the quantity of water conveyed by the Mis- 
sissippi equals but the tenth part of the whole quantity which falls in the basin 
of that river, contends that to explain this phenomenon it is necessary to sup- 
pose a drainage by subterranean passages, and attributes to that cause the foun- 
tains of fresh water observed in the sea at the mouth of the river. M. de Saus- 
sure cannot admit that these fountains proceed from cavities or clefts in the 
middle or superior portion of the river, which flows over the old sandstone, 
quite unconnected with the recent formations of New Orleans. M. Chaix dis- 
putes even the basis of M. Thomassc’s hypothesis. Not only is it very diffi- 
cult accurately to gauge the river at different seasons, but we are by no means 
in possession of the necessary elements for estimating, even approximately, the 
quantity of water which falls in the basin of the Mississippi. M. Chaix reminds 
us that M. Ellet gauged that river both below and above each of its great afilu- 
ents, and that the result showed that the quantity of water conveyed, though 
augmenting considerably at each point of confluence, regularly presented a sen- 
sible diminution fifty leagues lower down. This diminution, according to the 
engineer just mentioned, is easily accounted for when we observe that below 
the Arkansas the right bank is low, swampy, and furrowed by bayous or arms 
of the river. 
The natural glaciers of our mountains have been the object of very particular 
investigations by MM. Soret and 'Thury—by the former in reference to a glacier 
above ‘hun, and by the latter in the case of the Pré de St. Livres, in the vau- 
dese Jura, and in that of Vergy, in the Alps of Savoy. It was in winter that 
M. Thury made the visits of which he gave us an account, and he draws from 
his observations the conclusion that the time of the formation of the ice in these 
cavities must have been the season of the year when both water and frost pre- 
vail—that is to say, in autumn, and especially in spring. 
Professor de la Rive presented to the Society copies of three Portuguese 
maps of Africa, of an earlier date than 1558, which were sent to him by M. 
Lavradio, for the purpose of showing that many geographical facts discovered 
within late years were not unknown at the above epoch. M. Chaix, in effect, 
called attention to the singular fact that these maps indicated a chain of lakes 
