476 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



1. That if any physical cause increase the tenacity of wire, 

 but increase the product of its elasticity and linear density 

 in a more than duplicate ratio, it will render it more liable to 

 break under a blow. 



2. That the fracture of a wire depends on the length, its 

 support, and the method of applying the blow. 



3. That in cases such as surges on chains, etc., the effect de- 

 pends more on the velocity than on the momentum, or vis 

 viva of the surge. 3 A, December 23, 1871, 492. 



keenan's boiler coating. 



Much value is assigned to a substance known as Keenan's 

 Boiler Coating, as a means of preventing the radiation of heat 

 from steam-boilers, and the saving, in consequence? of fuel as 

 well as of time in bringing steam up to the proper degree 

 of tension. The substance is a pulp composed of paper, oil, 

 and certain chemicals, and is laid cold on boilers, steam-chests, 

 steam-pipes, or any other article that is to be protected from 

 the outer atmosphere, to the thickness of an inch and a quar- 

 ter; on superheaters two inches are required. The boiler, 

 however, must be kept warm during the coating process. 

 When the pulp has properly set it receives three coats of 

 paint, and can, if necessary, be grained, and made to look or- 

 namental. 



The editor of the London Mechanics' Magazine has recent- 

 ly examined certain boilers coated with this substance, and 

 found that, with boilers in actual operation, the exterior ex- 

 hibited a gentle warmth just perceptible to the touch. He 

 also was informed that it was the practice of the stokers to 

 draw their fires at half past three in the afternoon, and to close 

 the dampers, the steam being then at about thirty-five. On 

 resuming work in the morning, at 5 o'clock, the gauges gener- 

 ally showed twenty-five pounds of steam, or a loss of only 

 ten pounds during the night as the result of radiation. 3 

 A, January 13, 1872, 31. 



ASBESTOS FOR PISTON-RODS. 



The use of asbestos as a piston-rod packing is now enga- 

 ging the attention of engineers. It is stated that friction has 

 no appreciable effect on this substance, and, however great 

 the pressure of steam, or however high the temperature may 



