MISCELLANY. 
263 
diaphragm, it is no longer possible to use it ; as when lighted, the flame 
passes through the fracture, and communicates with the flame at the bot- 
tom of the cylinder, which then burns like an ordinary gas light, and 
like it, would blacken the surface of any cold body presented to it. The 
wire cloths, if not broken through by violence, will last for months al- 
though in daily use; and if covered by a layer of coarse sand or pounded 
lime stone, will continue serviceable for an unlimited period. 
When more intense heat is required than is attainable by the unaided 
combustion of the mixed gases, recourse may be had to various forms of 
blow pipes ; and when a large volume of such flame is to be employed, 
the current of atmospheric air may be urged by double bellows. A. very 
efficient apparatus on this principle is to be seen in the laboratory of Dr. 
B. Reid. 
It is to be regretted, that such applications of gas are not more general- 
ly known and introduced into work shops, as there are numerous processes 
in the arts in which they would afford facilities to the workman which 
he can scarcely command by any other means. For example, in the hard- 
ening of steel tools, it is well known that a piece of bright steel, when 
heated to redness in a forge or muffle, is subject to oxidation and that a 
black scale remains after hardening, which it is difficult to remove without 
some injury to the work, as in the case of a screw tap ; whereas, if the 
same piece of steel be heated in a flame of the mixed gases, where there 
is no free oxygen to attack its surface, it may be made and kept red hot 
without injury to its finest edge; it will be discolored, but without losing 
much of its polish. The artist has also the advantage of a distinct view 
of the article while it is being heated, and the power of withdrawing it 
from the flame the moment it has acquired the proper color, which, in the 
hardening of cast steel cutting tools, is of great importance. 
Many attempts have been made to apply carburetted hydrogen and pure 
hydrogen gases to the purposes of warming buildings, and various forms 
of stoves have been proposed, on the understanding, it would appear, that, 
by applying the flame of the gas to the metallic bodies an increased de- 
gree of heat would be communicated by them to the atmosphere around. 
A little consideration will show, that however the distribution may be 
modified by such contrivances there can be no increase of the heating 
power ; and that when a certain measure of gas is fairly burned, the heat 
evolved into the apartment will be the same whether the flame be dispos- 
ed as a light, or made to play against metallic plates or other combinations 
of apparatus. In all cases where the products of combustion are allowed 
to mix with the atmosphere of the apartment, without provision being 
made for carrying them off by ventilation, the effects of such processes 
must be more or less deleterious to health, according to the proportion 
these products bear to the mass of air they mix in. On the whole, it may 
be assumed, that this mode of heating apartments is the most expensive, 
