618 THE POPULAR SCIENCE MONTHLY. 



Experimental tests were made with several partition walls, to ascer- 

 tain how thin it would be advisable to construct them where the load 

 was small. The result of the experiments showed that the resistance 

 of partitions eight feet in height made of beton two and a half inches 

 thick, and re-enforced with one-quarter-inch iron rods, was equal to 

 brick walls eight feet high, and eight inches in thickness. 



It is the opinion of the writer that for the great majority of houses 

 required for dwelling purposes, a system of thin re-enforced double 

 walls, with a space of from six to ten inches between them, and re- 

 enforced cross-connections every two or three feet apart, to unite the 

 outer and inner walls firmly together, could be built up to thirty or 

 forty feet in height, at a cost not exceeding that of first-class brick- 

 work. 



Besides an equal economy in the construction, such double walls 

 would be an incomparably better defense against stormy weather than 

 the best quality of brick-work, because the absorjDtive capacity of 

 beton is so much less than that of brick. 



Thus, all things considered, the thin double-wall system commends 

 itself as embodying the desirable qualities, essential to the outer and 

 inner wall construction of dwelling-houses, furnishing as it would 

 a sure protection against both fire and dampness, and the means for 

 thorough ventilation. Besides the special fitness of the re-enforcing 

 system for floors, roofs, beams, and thin walls, it is an interesting 

 question whether the same system may not be also applicable, and ad- 

 vantageously extended, to a more general use in many engineering re- 

 quirements especially in situations where immense weights must be 

 sustained, and where iron construction alone is difficult of application ; 

 notably in such an important work as the Hudson River Tunnel, where 

 its tubular form is constructed with an outer cylindrical shell of flue- 

 iron, and lined inside with heavy brick mason-work. Much of this 

 tunnel rests upon a treacherous bed of silt, and might be made abso- 

 lutely safe from rupture by settling, induced by vibrations resulting 

 from railroad traffic in addition to its own weight, by adding to a thin 

 brick lining a strong beton sixteen or eighteen inches thick, which 

 should include three or four courses of iron bars, of suitable size, 

 laid longitudinally and in sufficient number to bear any amount of 

 strain that might be brought upon it. Rings of flat bar-iron, inter- 

 spersed in the bcton-lining a few feet apart, would further add to 

 its security. 



The re-enforced beton system has also been employed with ad- 

 mirable results, in heavy foundations, for stationary engines. The 

 writer, three years ago, mounted a two-hundred-and-fifty-horse-power, 

 tandem, compound engine, of very heavy pattern, on a re-enforced 

 beton-bed, twenty-three feet long, five feet wide, and seven feet deep. 

 It is apparently as firm and hard as a single mass of granite of those 

 dimensions. The outboard bearing of the main shaft is also mounted 





