104 On Crystallization. [Aves 
dually... The solution in open phials has.sometimes cooled down to, 
the temperature of the cold water (about 40°), and has then re~ 
mained fluid in it for two or three hours; it has then sometimes 
crystallized in the soft spongy mass ; at others in firm, well formed 
regular crystals. 
15. Four or five phials have burst in which spontaneous regular 
crystals had formed, and over which subsequently a sudden consoli- 
dation of the residuary solution had taken place, after the change 
of colour was effected in the first crystals (as mentioned in No, 12), 
but whether from an expansion in the first or second crystals, I 
know not, as | was never present when this occurred.* I have 
never seen this fracture of the phial when only the regular crystals 
had formed, nor-when only the spontaneous solidification took 
place. It is probably, therefore, somehow connected with the ab- 
straction of the water of crystallization from the regular by the 
spontaneous spongy mass. In the above instances the crystals which 
had formed regularly were perfectly white, and were readily sepa- 
rated from the superior spongy ones by a little water gently poured 
over them, leaving them of the most perfect regularity, and forming 
a beautiful white crystalline preparation easily preserved, and not 
efflorescent, as in common cases. 
In all the cases thus enumerated, such are the anomalies pre- 
sented as to prevent my drawing one conclusion from them which 
could give me any insight into the causes that produce them. In 
some cases atmospheric pressure seems to operate, in others not ; 
agitation sometimes, but not invariably. The whole series of ex- 
periments is so interesting, I trust this account may lead to further 
investigation, which may finally afford an explanation, and possibly 
lead to new views on the subject of crystallization generally. I can 
only add, that I never could promise myself, 4 priori, that any one 
case should’certainly turn out as I expected; it appeared a matter 
of chance in a great degree, whether this or the other result should 
ensue. Tf 
* Tapprehend it must occur during the abstraction of the water of crystalliza- 
tion from the primary by the secondary crystals, which must be accompanied by a 
correspondent expansion. ‘ 
+ In speaking of the effect of atmospheric pressure on saturated solutions of 
salts, Dr. Higgins details an experiment which he made in a narrow-necked glass 
mattrass of three gallons dimensions. [t was fixed in a vessel filled with a satu- 
rated solution of sea salt: asolution of 144 oz, of Glauber’s salts in 96 oz. of 
water, in a separate vessel, was filtered into the mattrass, which was filled two- 
thirds by if, and the whole was made to boil so as to exclude the air by the vapour 
formed, Astrip of wet bladdersecured the mouth of the mattrass, and sustained 
the atmospheric pressure, 
Two mattrasses were thus prepared; they stood three days at a temperature be- 
tween 40° and 50°, and were often shaken without crystallizing ; as soonas the 
bladder was cut a few small concentric spicular crystals formed, and shot rapidiy 
through the liquor till it was almost solid: the caloric evolved, raised the tempera- 
ture from 60° to 90°, and in one experiment from 40° ta 90°, 
From this experiment connected with these above detailed, as also from man 
_ well-known facts, I am impelled te deny the perfection of Dr. Black’s celebrated 
theory of Jatent heat. It will be observed that boiling saturated solutions ef 
