342 
Some Account of Mandu, 
[Nov. 
volume, p. 634, of his Treatise on Physics. The numbers which we present as the 
result of observation are, in reality, deduced from the formula of M. Biot. To 
express them according to our law, we must make V, which here represents the 
radiation, equal to 
4,24 {at — 1) 
t being the excess of temperature of the vessel, and a a constant, the value of which 
we have determined to be exactly 1,0077. 
Value of t. 
Observed 
value of V. 
Calculated 
value of V. 
200° 
15°, 33 
15°, 29 
180 
12 ,51 
12 ,52 
160 
10 ,09 
10 ,15 
140 
8 ,04 
8 ,U 
120 
6 ,30 
6 ,36 
100 
4 ,84 
4 ,86 
80 
3 ,60 
3 ,58 
60 
2 ,54 
2 ,47 
The remarkable agreement found here also between calculation and observation, 
furnishes a new proof, that the number a depends neither on the mass, nor on the 
state of the body as to surface, since we again find, and under circumstances so 
very different, the same value, as in our experiments ou cooling in vacuo of vitreous 
and silvered surfaces. 
We may easily deduce from the expression for the rate of cooling in vacuo, the 
relation which connects the temperatures with the times. In fact, in designating 
the time by x, we shall have 
V= V — — = M (at — 1) 
dx 
M being a constant coefficient, which depends solely on the temperature of the sur- 
rounding mass. We may deduce then 
— . d t 
d X ~ M {at— T) 
1 / at — 1 \ 
and x = ■ ( log. -f- constant. 
M log. a \ at / 
The arbitrary constant, and the number M, will be determined for each particular 
case, after the values of t are obtained, corresponding to two known values of the 
time x. 
If we suppose t so small, that considering the value of the logarithm of a , we may 
confine ourselves to terms of the first power in the developement of at, we shall 
again have the law of Newton. 
Ill — Some Account of Mandu , an Ancient Hindu City. 
To the Editor of Gleanings in Science. 
Sir, 
Mandu, a ruined city of prodigious extent, near Indore, and the former capi- 
tal of Malwa, has never, I fancy, been so accurately described, as its truly magni- 
ficent remains would appear to deserve. Situated in a remote province, and dis- 
taut from the road of the passing traveller, few, beyond tho.se resident in the neigh- 
bouring cantonment of Mhow, have the opportunity of witnessing as melancholy 
a specimen, of what that great destroyer, time, has effected, as the face of the wide, 
habitable globe perhaps presents. Whilst far less interesting spots are almost daily 
receiving notice in some publication or other, the desolate state, and tenantless 
streets and Bazars of Mandu, once busy with the hum of trade and business, seem 
