C 1 
as this, is a very great curiofity. It is compofed of 
different laminae, and its figure is that of an oblate 
l'pheroid, whofe greated diameter is eight inches and 
an half; its leffer eight inches. It furface is ex- 
tremely regular, but appears in feveral of its parts, as 
though it had been corroded by fome acrid men- 
ftruum ; and in a place or two, where the external 
lamina is quite worn away, and the lamina imme- 
diately underneath it polifhed during its continuance 
in the mare, the calculus has great refemblance in 
colour to occidental bezoar. 
This done weighed in air fifteen pounds twelve 
ounces avoirdupois j in water fix pounds : fo that its 
fpecific gravity to that of water is nearly as eight to 
live. And you may obferve, that it is not only confi- 
derably lighter than any foffile petrifaction, but much 
more fo than many animal } fome human calculi, * 
when frefh extracted, being to water as two to one. 
With regard to its bulk, it is the larged I remem- 
ber to have been obferved, except one prefented to 
the Royal Society in the year 1 737, which was taken 
out of the domach of a dray-horfe, belonging to Sir 
Henry Hicks, Knt. at Deptford, and which weighed 
nineteen pounds avoirdupois, exclufive of the out- 
ward fhell or crud, which was broken off in feveral 
pieces. Both thefe dones were in appearance like a 
pebble, and formed of different lamina?. The greated 
circumference of that you fent me was fomewhat 
more than twenty-fix inches ; that of Sir Henry 
Hickes’s twenty-eight. 
Sir Henry Hickes’s horfe was twenty-two years 
old ; and, for eleven or twelve years before he died, 
frequently was obferved to be in violent pain : but 
5 I the 
