Mineralogy and Geology. 269 
by La Metherie in the Journal de Physique, xvii, 251-3; xlii, -1923. alii, 
355; xlviii, 66; Ixxi, 172, 382; Ixxviii, 241; Ixxxi, 288; and in his 
Theory of the earth in 1795 and his Lessons on Geology; also by 
Oken in his Lehrbuch der Naturphilosophie, 1809, pp. 149, 154;. by 
R. Jameson, Mem. Wern. Nat, Hist. Soc. Edinb., 1814, ii, 221—p. 
273, March 17, 1851. , * ihe howe 
n a Hydrobarometer, a new instrument for ascertaining the depth 
V M 
the jetting of the waters, six maxima thermometers (‘“ thermometers a 
maxima a déversement” of M. Walferdin*) protected from pressure 
and sunk to.a depth of 505 meters, indicated as the mean temperature 
26°'43 C. A seventh thermometer at the same time was sunk, unpro- 
tected from the pressure, and it indicated 39°50 C. A pressure of 
r 
This experiment was performed by Arago and M, Walferdin. 
It hence follows that a minima thermometer, protected from the 
action of pressure, will indicate the true temperature of depths; while 
a maxima inverting thermometer exposed to the pressure, and sunk with 
the other, may indicate the pressure of the sea. Such is the principle 
upon which M. Walferdin constructs his new instrument which he calls 
a hydrobarometer. 
ter, according to careful trials, is by enclosing .the.instrument in tubes 
of glass, more or less thick according to the pressure they will have to 
ards the Araxes. rarat viewed on the side of the Araxes is a 
broad-backed mountain of imposing grandeur owing to its breadth and 
the wild features of the crater shaped-cavity it encloses; while on the 
other sides it has the regular form of a pointed cone. dian’ 
Sa cece ee 
*Mw point with a and 
the ine f te t tion of ure is shown by the amount of mer- 
wo ra) mperature or action 0 press sagan race observes, is easily 
; and after the experimen 
ture, when the aquaiitity of m 
