64 On the Quantities of Heat developed in 
do not think it beneath the notice of your Journal, I will pro- 
pose to the sagacity of your readers to discover. I know that it 
is rather cut of fashion to offer these sort of questions to the 
public, though it was very common m the beginning of the last 
century, and was, I believe, attended with much advantage to 
science, by producing a widely extended emulation: even the 
questions yearly proposed in The Ladies’ Diary are, I am per+ 
suaded, very advantageous to the studious in mathematics. 
The “question I propose is this : 
Of any cube number under a million give the figure of the 
anit, the two last figures, and the number of places, mstantly 
and without any aid of writing to name its cube root. For ex- 
ample, let the cube 438976 be the number whose root is to be 
named. Given, the two first figures 43, the last figure 6, the 
number of places six. The root is to be immediately named. 
Should the ingenuity of some of your correspondents not find 
out the very simple method of doing this, I will with great plea- 
sure communicate it to you for insertion when required. 
I do not pretend that there is much use in this, but it may be 
an object of curiosity to some of your numerous readers. 
1 am, sirs, your obedient servant, 
H. C. ENCLEFIELD. 
To Messrs. Nicholson and Tillach. 
XVI. On the Quantities of Heat developed in the Condensation 
of the Vapour of Water, and in that of Alcohol. By BEn« 
JAMIN Count RuMrorD*. 
$1. Of the Quantity of Heat developed in the Condealion 
of tke Vapour of Water. 
Hay ING filled the calorimeter and steed it on its stand, a 
current of vapour was introduced into the serpentine through a 
cork placed in the lower aperture of the serpentine. This cork 
having been perforated with a hole two lines in diameter, in the 
direction of its axis, a small cork (two lines in diameter and two 
in height) was fitted into it, and four other holes about a line in 
diameter, pierced horizontally through the sides of the large 
cork at two lines below its upper extremity, and communicating 
with the hole two lines in diameter in the axis of this cork, af- 
forded a passage to the vapour, to admit of its entering by four 
small channels horizontally i into the serpentine. 
As the apertures of these small channels were higher than the 
level of the flat bottom of the serpentine, the water which re- 
* This paper was re ad before the French Institute as a supplement to 
the Count’s Inquiry into the Heat developed by Combustion, Vide Phil. 
Mag. voi. xlii. p. 296. 
sulted 
Ss 
