Chemastry and Physics. 133 
me dmgae If. It is required to tracd the effect of an unusuall 
req y 
day on the cone — erature of such a mass of roc 
ye 5 . It is required to trace the a effect conse- 
quent on a sudden sigan of mean temper 
Problem It is required to determine shes change of tem- 
perature within a ball of the rock, consequent upon suddenly 
removing it from a fluid of one constant temperature and plunging 
it into a fluid maintained at another constant temperature, 
Thomson contines himself mainly to the mathematical discussion 
of problem I, since the solution for problem I can be applie with 
side a mass of uniform trap roc. h extends up indefinitely 
in all directions on the other by is infinitely ted for an tn- 
Jinitely short time, and the whole is instantly and forever 
after maintained at a constant temperature. It is required to de- 
termine the consequent internal variations of temperature.” 
From the mathematical expression obtained from this statement 
the following conclusions result. 
1) The simultaneous ate aE at different points equi- 
distant from the position of the fire are simply ‘da es tional to the 
distances of these points from the plane surfac 
*) The law of variation of temperature with distance in any 
or ne line ES the place where the fire was applied, is the same at 
a 
)" w of vera of temperature with time is the same 
at a points of the s olid. 
7 
corresponding times in the law of a with time are propor- 
tional to the squares of the distance 
5 € maximum value of the Gancaracals: in the law of varia- 
tion with distance, diminishes inversely as ae square of the in- 
creasin ng t 0 
6) The maximum value of the sapineentiirs in the law of varia- 
tion with time, at any one point of the rock, is inversely as the 
fourth power of the distance from the Seah: "where the fire was 
applied, 
sl the fire was eal to a maximum at a ge oe ca to 
WV 2k, and brady oe that falls to zero at an infinite dista in 
every direction, The value of & for the trap rock of Calton Hil 
Am. Jour, Sor Tame Sn Vou. XVI, No. 92.—Aveust, 1878, _ 
ef 
