174 FF. W. Clarke on the Atomic Volume of Compounds. 
larger than the year. A precession is a good one. Instead of 
cumbering a line of page with bewildering cyphers we can say 
40, 100, or 1,000 precessions. Thus 40 precessions (and forty is 
a number easily remembered) would, by another felicity of this 
period, make a million of years, with a little over. We might 
call it a millionade, and give that again multiplications to form 
an age. An “age” might be 400 precessions. 
Should we adopt any thing like this plan, we should have the 
same delightful surprise which we often experience, by finding 
that ancient races and nations have been along the same path- 
way which we imagined ourselves to be for the first time break- 
ing and exploring. Six days, such as are His, who in His times 
as in His nature, must be what others are not; six immense 
West Point, June 7, 1870. 
Art. XVIII.— Upon the Atomic Volumes of Solid Compounds ; 
FRANK WIGGLESWORTH CLARKE, 8.B. 
IN studying the atomic volumes of solid compounds, the 
materials at my command have been in some respects quite co- 
pious, and in others quite limited. Having been unable, through 
lack of opportunity, to make any new determinations of spe- 
cific gravities, I have been forced to content myself with the 
ta which are scattered through the various scientific publica- 
studied with much certainty; while for other compounds only 
single observations of specific gravity have been made, and 
these often with no pretence to ngid accuracy. 
Here then at the very outset is a difficulty. If a substance 
has a very low specific gravity, and a very high atomic weight, 
