MECHANICS AND USEFUL ARTS. 69 



to granite, the author states that this stone is also, according to 

 the experience of Egyptian engineers, far more readily affected 

 by a moist climate than one would be led to believe. The obe- 

 lisk of Luxor, brought from Upper Egypt to Paris, has become 

 blanched and fall of small cracks, during the 40 years it has stood 

 on the Place de la Concorde ; although 40 centuries had not per- 

 ceptibly affected it as long as it was in Egypt. Granite in a 

 moist climate becomes the seat of a minute cryptogamic plant, 

 which greatly aids its destruction ; and it is, moreover, a well- 

 known fact, that the disintegration of this stone, which is com- 

 posed of 3 separate minerals (quartz, mica, and feldspar), de- 

 pends very greatly upon the thorough and intimate mixture, as 

 well as the chemical composition, of these 3 ingredients, each of 

 which, in a separate state, more easily withstands the influence 

 of the weather. 







PRESERVATION OP STONE. 



The preservation of brown sandstone, which has become so 

 popular as a building material, has also been the subject of exper- 

 iment ; and concrete building, as well as the manufacture of arti- 

 ficial stone, has been slowly but surely advancing. 



Our readers will recollect some editorial remarks upon the sub- 

 ject of " Improved Building Materials," published not long since 

 in this journal. The subject will bear further attention in connec- 

 tion with recent improvements. 



There seems to be a general effort now making to produce 

 cheaper and if possible better building materials than have hither- 

 to been employed. Our exchanges from abroad, more especially 

 those devoted to architectural topics, give us very encouraging ac- 

 counts of the progress of concrete building. This style of build- 

 ing seems growing in favor, and is furnishing a very goodclassof 

 dwellings at a very cheap rate. 



We find also an account of a new kind of artificial stone, called 

 the Victoria stone, which seems to have endured severe tests and 

 to promise well. 



It is the invention of a clergyman, Rev. H. Highton. The pro- 

 cess by which it is made consists in mixing broken granite with 

 hydraulic cement, and steeping the whole, when set, in a solution 

 of silica. The granite used is the refuse of the quarries, and is 

 broken up at the works. It is then mixed with Portland cement, 

 in proportions of 4 of granite to 1 of cement, sufficient water being 

 added to give it a pasty consistency. In this state it is placed in 

 moulds, when it consolidates in about 4 days. When taken from 

 the moulds it is placed for 2 days in a solution of silicate of soda, 

 which completes the process. 



The silicate solution is prepared in a peculiar manner, and upon 

 it the success of the operation depends. The silicate of soda has 

 the property of hardening any kind of concrete in which lime is a 

 component. This substance has been hitherto too costly for gen- 

 eral use in artificial stone manufacture, and it becomes caustic by 



