140 Association of American Geologists and Naturalists. 
Mr. R. admitted that in numerous conditions which are familiar to 
our observation, heated air or water was constantly displaced by that 
of lower temperature and greater density. In these common cases 
the colder portions of the fluid, by favor of associated conditions, find 
access below the warmer portions, and force the latter to a higher level. 
But in the great aerial and oceanic masses it is often otherwise; and 
the truth was that mistakes of importance have sometimes been made 
in relation to this matter. He thought all would allow, that there was 
no more innate tendency in heated air or water to rise than in. heated 
lava. An inferior stratum of heated water could not disobey the law 
of its own gravity, and might remain at the bottom of the. ocean for a 
length of time that no one could determine. 
Referring to another part of the paper of Mr. Dana— 
Dr. C. T. Jackson suggested that the conversion of pulverulent — 
into magnesian carbonate of lime, might have been effected by the 
tion of magnesian springs, containing bicarbonate of magnesia. He 
would ask Mr. Dana if any such springs existed in or around the coral 
islands of the Pacific Ocean, or if any sitiee9 of the mages existence 
of such springs could be traced. 
~ Dr. Jackson had witnessed with much interest Mr. Silliman’ ‘Ss anelysit 
of the corals, and of the magnesian limestone, formed from them, and 
it had occurred to him that a new theory of the formation of the mag- 
nesian limestones might arise from the facts observed by Mr. Dana. 
He was not entirely satisfied with M. Von Buch’s theory of cher 
Tasce I1.—Observations of Buchan’s Expedition. 
Temperature at ELOW THE SURFA ee 
surface. joe [= to Latitude and date. 
3g | 
Ea 34 30" From 79°.45 N. 
, a 34.5 35" to 80°.27 N., in| 
mers 34 60 June and July. 
34 34.5 72 
35.6 83 “ 
32 36 94 « 
32 35.3 95 & 
31.5 365 e : 
32 35.6 108 « 
30.3 36. 120 “ } 
30.5 36.5 142 3 ec 
: RS A 365. ot 173 “ , 
7 32.5 36.3 185 “e 
| 31.5 37 237 ‘ 
; 32.5 355.- 270 « 
= 35 331 “ 
— 43 700 Ee 
? 
Xpedition, 
a 
ce harbor, west side of Spitzbérgen, See Capt. Beechy’s narrative of the 
ee es ee 
