of American Geologists and Naturalisis. 113 
also found in a steam boiler and analyzed by Prof. Johnson. of 
wh 
As the boilers in which the scale was collected do not proba- 
bly use pressures exceeding fifty pounds per square inch, the tem- 
Pr perature must have been under 300° Fah. 
"hs In a geological point of view the observation possesses inter- 
x est, as it indicates in the water at different parts of the ocean, 
5 variable proportions of sulphate of lime, due probably to the same 
f os causes which in earlier periods occasioned so very unequal a dis- 
. gd - sypsum in different parts of the earth and even of the 
same co 
vt pas alan possibly have a bearing on the temperature of the 
aes or ocean at the time when the different sulphates of lime 
were deposited. These have commonly been divided into hy- 
S drous gypsum and anhydrite, but that the latter is not always 
ce destitute of water is proved by several facts. 
= - The statement of Dr. Beck was referred to as showing that the 
anhydrite of Lockport, New York, “contains sometimes a con- 
siderable proportion of water.’ 
-A-specimen of anhydrite a the East River of Pictou, Nova 
Scotia, had yielded Prof. Johnson essentially the same composi- 
tion as the boiler soak, Viz., 
fiir: > Lime mei OAD ne te atoms, 
BEY ay Sulphuric sai - 564-70 a 2 
Water, -90 1 
while a specimen of praia gypsum fom Plaister cove, Cape 
Breton, had given, 
‘ee. Lime - 32°9 - 1 atom, 
Sulphuric es 2 - - 463 - Le, 
- 20°8 . mh“ 
- [Prof. W. 'B. Rogers remarked that the gypsum in the southern 
rer of Virginia, in the salt region of that state, was all of the 
Same character as that of East River of Pictou, and of the boiler 
scale, containing two atoms of sulphate of lime to one of water.] 
i= Prof, Johneon.referred:to the fact stated by authors, that in cer- 
tain parts of Switzerland, particularly at Bex, canton rape 
‘the masses are formed by ‘hydrous gypsum toa certain sepiiion 
below that of saccharoidal anhydrite. 
__ He also referred to the fact, that common hyde ‘ous “gypsum 
‘to more than 300° is afterwards in neapable of absorbing 
water: so as to “set” in the process of stuccoing. ‘This renders 
it improbable that true anhydrite has been converted into com- 
ene psum by the action of water. 
Si pda y Prof. Henry. —Prof. H. showed the analogy 
between light and i ont by stating that as two rays of light might 
be so Os to produce darkness, so two rays of heat eet 
produce cold. The facts with regard to heat 
Savony § Senin, Cel. ¥, ta the OS 
