MODIFIED ly COMPRESSION. 135 
no longer exifts, having crumbled entirely to pieces, notwith- 
ftanding all the care I took to inclofe it with glafs and wax. 
Aprit 26. An experiment was made with fome carbonate 
of lime, purified by my friend Sir George Mackenzie. Two 
grains of water were introduced, but were loft, I fufpea, as in 
the laft cafe. The heat applied was 32°. The lofs of weight 
was 10.6 per cent. Yet, though made but one day after the 
laft-mentioned fpecimen, it remains as frefh and entire as 
at firft, and promifes to continue unchanged. The external 
furface, as feen on removing the lid of the conical cup, was 
found to fhine all over like glafs, except round the edges, 
which were fringed with a feries of white and rough {phericles, 
one fet of which advanced, at one fpot, near to the centre. 
The fhining furface was compofed of planes, which formed ob- 
tufe angles together, and had their furface ftriated’; the ftriz 
bearing every appearance of a cryftalline arrangement. When 
freed from the cup, as before, the fubftance moulded on the 
platina was found to have affumed a fine pearly furface. Some 
large air-bubbles appeared, which had adhered to the. cup, 
and were laid open by its removal, whofe internal furface had 
a beautiful Inftre, and was full of ftrie like the outward fur- 
face. The mafs is remarkable for femitranfparency, as feen 
particularly where the air-bubbles diminifh its thicknefs: a 
fmall part of the mafs being broken at one end, fhews an in- 
ternal faline ftructure. 
APRIL 29.—A>cup of platina was filled with feveral 
large pieces of a periwinkle * fhell, the fharp point of the 
fpiral being made to ftand upright in the cup, (fig. 30.). A 
heat of 30° was applied, and no water was introduced. The 
carbonate loft no lefs than 16 per ceut. The thell, particularly 
| , _ the 
.* Turbo terebra, Lry.. 
