i 9 4 THE POPULAR SCIENCE MONTHLY. 



made in strips twelve, sixteen, twenty, or twenty-four inches wide, to 

 correspond with walls made of three, four, five, or six courses of brick. 

 Its superiority to ordinary bitumen depends on the fact that it will 

 not crack, like the latter, from unequal settling of the walls. Damp- 

 resisting solutions are also sold for coating damp walls. 



Asphalt mastic is much superior to tar for roofing purposes, owing 

 to its fire-proof qualities, and its use for this purpose is rapidly increas- 

 ing. At the present writing it is being applied to the Welles Building, 

 at the lower end of Broadway. It is said that, when a building cov- 

 ered with such a roof burns, the falling roof acts like a blanket in 

 smothering and extinguishing the flames. 



Asphalt possesses another valuable property, that of absorbing 

 vibrations, and is hence useful for foundations of machinery running 

 at high speeds. A block of bituminous concrete weighing forty-five 

 tons formed the foundation of the Carr's disintegrator which made 

 fourteen hundred revolutions per minute at the Paris Exhibition. It 

 would seem to be especially adapted to serve as foundations for the 

 high-speed steam-engines used for generating electricity. 



Asphalt forms an excellent insulator for electricity, but, as other 

 and cheaper materials may be employed, its use will not be so exten- 

 sive in this field. 



The origin of asphalts is unknown, but several theories have been 

 advanced in regard to it. Professor J. S. Newberry believes that they 

 are the more or less perfectly solidified residual products of the spon- 

 taneous evaporation of petroleum. If we accept this theory (and 

 many do not), we are but one step nearer a solution of the problem, 

 for the origin of petroleum itself is still unknown. Some think that the 

 bitumen was formed first, and the limestone deposited in it ; others, 

 that the liquid bitumen was forced into the pores of limestone already 

 in existence ; while a third hypothesis assumes that they were formed 

 simultaneously, the bitumen from the organic matter, and the lime 

 from the shells of some ancient mollusks. The last-named theory 

 seems to have some support in the abundance of fossil ammonites met 

 with in the mines at Limmer ; the experimental attempts to impreg- 

 nate the rock artificially, as above described, render the second hy- 

 pothesis improbable, although its occurrence on the Dead Sea and in 

 Trinidad is in its favor. No explosive gases are met with in the 

 mines of Val de Travers, Seyssel, and Lobsann, so that open lights are 

 used ; but at Pechelbronn, a few miles from Lobsann, several explosions 

 have occurred. Although these were attributed to marsh-gas, they 

 were more probably due to the vapors of the lighter constituents of 

 petroleum, with which the bituminous sands of that locality seem to 

 be saturated. 



There are several circumstances which indicate that bitumen and 

 asphalt are more nearly related to petroleum than to coal-tar, and that, 

 whether asphalt was made from petroleum or not, they have a similar 



