PATENTS. 



outlet. The negatives laid in the two com- 

 partments are always covered by water, which 

 is constantly changed without subjecting the 

 films to objectionably violent action of the 

 water. 



Screw-Propeller Railway. This device, by J. R. 

 Gorman, an English engineer stationed in In- 



S= 



SCREW-PROPELLER RAILWAY. 



dia, was designed to overcome a very steep 

 gradient by acting as an assistant to an ordi- 

 nary engine The side-elevation only is illus- 

 trated herewith, that being sufficient to indi- 

 cate the principle involved. AB is a heavy 

 rail laid midway between the ordinary rails. 

 It is provided with raised projections like the 

 teeth of a saw. is an iron cylinder sur- 

 rounded by screw-threads of wide pitch, and 

 mounted on a suitable carriage. The distance 

 apart of the threads corresponds exactly to 

 that between the elevations on the central rail, 

 and these last have their upper faces adjusted 

 so as to bear upon the threads, and coincide 

 accurately with the pitch of the screw. The 

 problem of causing the cylinder to revolve is a 

 matter of mechanical detail that need not here 

 be entered upon. It is obvious that, when the 

 screw revolves, the carriage must move with 

 tremendous power. The speed is calculated at 

 six miles an hour. The mathematical calcula- 

 tions give one in ten as the gradient that this 

 screw-propeller engine is able, without diffi- 

 culty, to overcome; but this is probably an 

 underestimate. Its obvious superiority over 

 the ordinary cog arrangements for steep in- 

 clines are the smoothness of its action and 

 the safety guaranteed by the fact, that several 

 threads bear continuously upon as many differ- 

 ent teeth, so that if one gives way the others 

 are amply able to bear the additional strain. 



Water: to heat rapidly. It has long been known 

 that metallic vessels containing water, even 

 when subjected to the direct action of flames, 

 are surrounded by a jacket of cold air. This 

 may be easily proved by pasting a bit of pa- 

 per upon the bottom of the vessel. It will 

 often remain unscorched for a long time, even 

 when subjected to a fierce heat. Mr. Thomas 

 Fletcher recently read a paper on the subject 

 before the Gas Institute of Great Britain, in 

 which he showed that, by studding the bot- 

 tom of the boiler with coppor rods or rivets 

 four diameters long projecting below the ves- 

 sel and upward into the water, the process of 

 heating to the boiling-point was greatly accel- 

 erated. The cold zone is not removed by this 



device, but the lower ends of the copper rods 

 become heated and conduct the heat to the 

 water. In his experiments Mr. Fletcher boiled 

 a pint of water in a studded four-quart kettle 

 in h'fty seconds, while more than twice the 

 time was required in a kettle of the unim- 

 proved type. Studs of this description have 

 been used in a crude form in 

 this country and in England for 



H about twenty years, and with 



marked advantage; but Mr. 

 Fletcher claims that he has dis- 

 covered the true proportions 

 and secures greater efficiency 

 by using copper instead of iron, 

 as has usually been done with 

 iron boilers. 



Water-Motor. The motor il- 

 lustrated herewith was shown 

 at the Inventions Exhibition in London, and 

 the claim is made that it is more economical 



WATER-MOTOR. 



of force than any other motor. The best 

 turbines are averaged at about 70 per cent., 

 and undershot water- wheels are as low as 



