Royal Society of London. 215 
Mr. Cavendith’s ingenious experiments, and the calculations 
founded-on them. Thofe who feel themfelves interefted-in 
‘them will haye recourfe to the original account, We thall 
only mention the refult. By a mean of the experiments the 
denfity of the earth comes-out 5°48 times greater than a 
of water. 
By the experiments made by Dr. Mafkelyne on the at- 
traction of the hill Schehallien, the denfity of the earth was 
computed to be only 4{ times that of water, . 
A paper * by Mr. Home was alfo read, containing an ac- 
count of fome experiments made in order to afcertain the 
caufe of the light feen in the eyes of cats and fame other 
animals in the dark. After enumerating the opinions of other 
philofophers, he proceeds to fhew, that when the light was 
perfectly excluded from the room in which the cat was 
placed, the eyes were neyer obferved to fhine; whence he 
eoncludes. that the eye merely colleGts the light diffufed 
through the room. He then relates fome obfervations on 
the ftructure of the optic nerve. -Having diffected the eye 
of a cat juft killed, he was furprifed at finding the retina 
tranfparent. This indyced him, to repeat the experiment 
not only on cats, but alfo.on horfess and always with the 
fame refult, if the retina was examined immediately after 
death. But if this examination was delayed an: hour or 
two, it was opake and whitifh, as defcribed by anatomifts. 
‘The optic nerve, from the retina to the brain, feemed to be 
-compofed of bundles of fibres not parallel to each other, 
but alternately interwoven and feparated, the interftices 
filled with a tranfparent fluid, fo that a tranfverfe fection 
taken’ near the brain was nearly a circle containing about 
40 opake, round fpots; near the eye about 200 of thefe 
fpots, and in the middle about a: mean> between’ .thefe 
numbers.  Thefe-obfervations were es witha Bae algnee 
eet ing about 23 times, - 
‘ 
€ The C CroonlaniLeétures Sih eee ns 
