YOL. LXI.] PHILOSOPHICAL TRANSACTIONS. 215 



occupied by their interstices, as the surface covered by their circular bases, to 

 the surface covered by the interstices of their bases. That is, as 39 to 4, very 

 nearly, by the first problem. But the spheres contained within these cylinders 

 are each but -^ of the containing cylinder. The solid content therefore of all 

 the spheres is but -J of tlie solid content of all the cylinders; and the remaining 3d 

 part of the solid content of the cylinders, together with the interstices between 

 the cylinders, makes up the whole of the interstices between the spheres. There- 

 fore the space occupied by the spheres, is to the space occupied by their inter- 

 stices, as 39 — V to 4 -|- Vj or as 26 to 17, very nearly. 



The spheres being in the closest arrangement possible, if each be a solid atom, 

 or without pore within its own dimensions, then the infinitely thin crust, which 

 these atoms compose, is plainly the most dense that can be composed of equal 

 spherules, having their centres in one plane. And the space occupied by its 

 matter, is to the space occupied by its pore, as 26 to 17, very nearly. 



Scholium. If the component spherules, instead of being solid, be supposed to 

 be each of the density of gold, in which one half of the bulk may reasonably be 

 supposed to be pore ; then only 4- of the space, which they occupy, is filled with 

 matter, and the other half is to be added to the pore. Hence spherules of the 

 density of gold, arranged in the closest manner possible, having their centres in 

 one plane, compose a crust, in which, -J-4-5 or somewhat more than i^f, of its 

 bulk, is matter. Therefore, the density of such a crust is somewhat greater 

 than 1 2 times that of water, since ^ only of the bulk of water is supposed to be 

 matter, and 4-| is pore. 



N. B. The first of these two problems, enabled me to determine the greatest 

 possible number of spherical particles of a given magnitude, that could find room 

 to lie at one time on the surface of the sun; and by the 2d, I found the density 

 of the crust, which such particles, in the closest arrangement possible, with a 

 given density of each particle separately, would compose. 



LI. On the Going of an Astronomical Clock. By the Rev. Francis IVollaston, 



F.R.S. p. 559. 



Mr. W.'s clock was made by [Holmes. The pendulum rod is of deal, to 

 which the ball is screwed fast; and it is adjusted by a smaller weight under- 

 neath. The clock beats dead seconds; and is fastened to a principal wall, inde- 

 pendent of the floor. The room never has a fire in it. The transit telescope, 

 with which he made the observations, has an achromatic object glass, of only 

 14 inches focal length, and magnifies about 15 times; its transverse axis is but 

 12 inches long, and it is mounted on a vertical axis of 18; being designed for 

 an equal altitude instrument likewise, and so used in some of the observations. 

 It is fastened to a large stone pillar, bedded on the wall of the house; and is 



