44 ANNUAL OF SCIENTIFIC DISCOVERY. 



steam in vaporizing^ the more volatile liquid is obvious. But all 

 these vapors are highh" inlhinimablc, and in mixture with atmo- 

 spheric air they are explosive. The danufcrs attendant on their 

 use are therefore very great. Ammonia is neither inllammable 

 nor explosive, and if, by the rupture of a tube or other aeeident, 

 the solution should be lost, the engine will still operate with 

 water alone. 



The action of ammonia upon brass is injurious; but it pre- 

 serves iron iVom corrosion indelinitely. It contributes, therefore, 

 materialh- to tiie durability of boilers. A steam engine may be 

 converted into an ammonia engine by replacing with iron or steel 

 the parts constructinl of brass, and by modifying to some extent 

 the apparatus of condensation. 



ELECTRO-HEATING APPARATUS. 



This invention, patented March 12, 18G9, is based upon the 

 well-known lact that electricity, in passing through a conductor 

 of insullicient capacity (such, for instance, as a wire of very 

 small diameter), evolves or develops heat. It is also well known 

 that a wire of any great length, and of sufficiently small size to 

 evolve considerable heat, will not conduct a strong current of 

 electricity without difficulty and loss, and that as the wire be- 

 comes heated, its non-conductivity is increased, and that, in con- 

 sequence, the heat becomes so great that the wire will b(; fused. 



The object of the invention is to obviate this difficulty, by ena- 

 bling a strong current of electricity to pass through a heat-evolv- 

 ing apparatus of any length ; and to this end it consists in providing 

 an electrical conducting coil, or chain, with intervals of /mall 

 conducting power, in traversing which the electricity will be 

 caused to evolve heat; and further, in interposing between said 

 obstructing intervals free conductors of much larger size, which 

 constitute reservoirs of electricity and radiators of heat, and will 

 elfectually obviate the difficulty experienced in a continuous length 

 of conductor of insufficient capacity. 



In this application of the invention, namely, for railway car- 

 riages or cars, it is proposed to employ magneto-electric machines, 

 constructed especially for this purpose, for producing the requi- 

 site current, placed, if necessar}', under the car, and to obtain the 

 power to operate them from the axle of the car, — tims taking 

 advantage of a motive power which already exists, but of which, 

 lieretofore, no use has been made. 



A machine capable of heating to incandescence one foot of 

 platinum wire one-tenth of an inch diameter, will heat 100 feet 

 one-hundredth of an inch ; 200 feet, two-hundredths of an inch, 

 etc. ; the law being that the lengths of the wires vary inversely in 

 proportion to the s<iuares of their diameters. Now, to reduce this 

 to practice, it will be seen that a machine or battery of the power 

 above referred to will heat a length of coil or chain, in which the 

 aggregate length of the small wire of one-hundredth of an inch di- 

 ameter, forming the obstructions, is 100 feet; and 200 feet, if their 



