MECHANICS AND USEFUL ARTS. 39 



other vegetable mattevs. The process is very simple : a thin 

 coating of slaked lime made into paste with water, or whitewash, 

 is laid on the object to be silicatized, and, when this has been al- 

 lowed to dry, silicate of potash is applied over the coating ; the 

 effect, it is asserted, being that all the portions touched by the 

 solution of potash become completely insoluble, and of very great 

 adherence. In order to obtain adi insoluble silicate in the interior 

 of a substance, all that is necessary is to impregnate it by im- 

 mersing it in whitewash or lime-water, and, when it is dry, to 

 steep it in a solution of the silicate of potash. 



By this means it is proposed to prevent the decomposition of 

 vegetable substances by petrifying them ; also, to protect po- 

 rous building-stones and brick against air and damp; iron, by a 

 coating of jjaper, pulp, or other finely-divided woody matter, 

 mixed with slaked lime. 



Again, letters, characters, or any other device, can be traced 

 with the silicate on any surface spread with lime ; and those y>ov- 

 tions touched by the silicate will alone adhere and become insolu- 

 ble. Or, if they be traced with a solution of gum arable, and the 

 whole be washed over with the silicate, the parts protected by the 

 gum can be washed off, the rest remaining in relief, as the let- 

 ters, etc., do in the first place. 



The process seems to be substantially the same as the Eng- 

 lish process known as Ransome's. — Scientific American. 



A NEW CEMENT. 



A late number of the " London Engineer" announces a new 

 cement of great value, which is introduced under the euphonious 

 title, " The zojiissa iron cement," which, it is claimed, is capable 

 of joining any two solid substances, however dissimilar. Wood, 

 brick, iron, stone, or glass, can be inseparably united with equal 

 facility. A series of experiments, witnessed by the "Engineer," 

 gave the following results : — 



Plates of glass were firmly joined, edge to edge ; ordinary 

 bottles stuck upon the wall resisted all atteiiipts at sepai-ation, till 

 the stone yielded. Chami?agne bottles, cemented laottom to bot- 

 tom, sustained a weight of 250 jjounds. Two bricks remained 

 joined under a tension of 325 pounds, till the brick itself frac- 

 tured, but the cement remained firm. Brick-work cemented with 

 this has the solidity of a granite slab. 



With paper treated with this preparation in solution, the in- 

 ventor has made air and water-tiglit tubes, ammunition cases, 

 coffins, and even constructed a house, one story and a half in 

 height, perfectly wind and water tight, which he has now on 

 exhibition. 



Of the constitution of this cement, or the expense of manufac- 

 turing it, the "Engineer" makes no intimation. 



HARD HYDRAULIC CEMENT. 



The following receipt is given for a cement, which, it is said, has 

 been used with gi'eat success in covering terraces, lining basins, 

 soldering stones, etc., and everywhere resists the filtration of 



