$02 Researches upon the Heat developed 
ture which it is possible to procure by means of combuse 
tion. 
We have seen that, according to the results of the re- 
searches of Mr. Crawford, it seems that when one pound 
of hydrogen is burned, enough of heat is developed on 
this occasion to elevate the temperature of 410 pounds of 
water to 180° of Fahrenheit (= 100 degrees centigrade.) 
Now as one pound of hydrogen perfectly dry, is united 
by burning to 7°3333 pounds of oxygen, and forms with it 
8°3335 pounds of steam, it is evident that the quantity of 
heat which exists in 8°333 pounds of steam at the instant when 
this steam is formed, is equal to that which is necessary to 
raise the temperature of 410 pounds of water 180° F., or to 
elevate the temperature of 73°800 pounds of water one de- 
gree of the scale of Fahrenheit. 
From this calculation we may conclude that the quantity 
of heat which exists in one pound of steam, at the instant 
when it is formed, is sufficient to raise the temperature of 
one pound of water 10063 degrees. 
If the capacity of the steam for heat was equal to that 
of liquid water, it is very certain that the temperature of 
the vapour at the instant of its formation would be that of 
10063° F. s 
In order to form an idea of this degree of intensity, we 
may compare it to.an intensity of heat which is known. 
A piece of iron heated until it becomes red even in day- 
light, has then the temperature of 1000° F.; consequently 
the temperature of the steam at the instant of its formation 
would be ten times higher than that of red hot-iron: but 
as, according to Crawford, the capacity of the steam for 
heat is greater than that of water in the proportion of 1°55 
to 1, the temperature in question will be less than that of 
10u63° in the same proportion, It will therefore be equal 
to 8750° F. 
Here therefore is the limit of the intensity of the heat, 
in the midst of the greatest fire, in which pure hydro- 
gen would be employed as a combustible, and in which the 
fire would be fed by pure oxygen. This is an intensity 
which we may approach more or Jess, but which we can 
never attain. ; 
As Wedewood’s pyrometer indicates much higher 
temperatures, it seems demonstrated by the result of this 
calculation that the scaie of this pyrometer is faulty. These 
doubts have been stated by other chemists. 
But in order to decide definitively upon this interesting 
question, 
