Of Bones . 23 
drawing the firing R S gently, and then making it faft 
■by the peg T. 
After which place the frame to the microfcope, as 
above directed 5 and you will have a beautiful profpedt 
of the circulation, if viewed through the microfcope 
upon a table; but much more fo if you apply it to the 
folar apparatus. 
I hope by this time the reader will be enabled to fix 
any other fubjedt of the like fize to the apparatus, in 
order for difle&ion, and alfo be ready at applying them 
to the microfcope, either to be looked at by the eye 
through the magnifiers, or caft upon .a fcreen when ap¬ 
plied to the folar apparatus. The reader will alfo per¬ 
ceive that none of the modern microfcopes are fo capable 
of having all forts of fubje&s applied .to them, as thefe 
are in an apparatus, fo eafy in its ufe, as to give gen¬ 
tlemen as little trouble as poflible in the application of 
all forts of objects. 
Of Bones. - 
T HEIR fuperficial part is found to confift of a 
vaft many fmall veftels, and fome few of a larger 
fize; which laft, when they came to the furface of the 
bone, appeared to Mr. Leeuwenhoek either with a 
membrane, or bony fubftance, perfectly tranfparent: he 
once difcovered four or five vefiels in a fmall piece of a 
fhin bone of a fufiicient fize for a fingle filament of filk 
to pafs through them, and one of them feemed to him 
to have a valve 1 fo difpofed as to admit nothing into it, 
but only to let out what was therein contained. 
The fpongy or cellular fubftance on the infide of the 
bone confifts of long particles clofely united, that are 
C 4 made 
* 
► . i Phil. Tranf. No. 366. 
