MECHANICS AND USEFUL ARTS. 45 



under the tower could be rated with exactness. It has been by 

 this means that the alignment has been tested from time to time, 

 and the proof of the correctness of the system has been established 

 by the present result. Scientific American. 



IRON STONE. 



At a point in the Thames, where an eddy accumulates a shoal 

 of sand, agglutinating iron springs rise from beneath, and pro- 

 gressively convert the sand into rock, which has to be removed, 

 from time to time, by blasting. Bourne, the engineer, con- 

 ceived from this circumstance the idea of turning quicksands to 

 firm foundations by a similar process, and actually proposed to 

 do this for the railway bridge over the Soane in' India. Quick- 

 sands at this point, as deep as borings had been made, were to be 

 converted into rock by injecting them, through perforated pipes, 

 with sufficient iron water, from a hill of iron pyrites near at hand, 

 to stick together the whole mass. The line of the road was 

 eventually altered, and the bridge was built at another point; but 

 Mr. Bourne still believes that an expedient of this kind will be- 

 come a valuable feature in engineering. 



DURABILITY OF TIMBER. 



In situations so free from moisture that we may practicalh 7 " call 

 them dry, the durability of timber is almost unlimited. The" roof 

 of Westminster Hall is more than 450 years old. In Stirling Cas- 

 tle are carvings in oak, well preserved, over 300 years of age. 

 Scotch fir has been found in good condition after a known use of 

 300 years., and the trusses of the roof of the basilica of St. Paul, 

 Rome, were sound and good after 1,000 years of service. The 

 Builder. 



CEMENT TO FASTEN IRON IN STONE. 



A German professor has found out a cement for fastening iron 

 in stone, which in 48 hours becomes nearly as hard as the stone 

 itself. . This consists of 6 parts of Portland cement, 1 part nicely 

 powdered lime, burnt but not slaked, 2 parts of sand, and 1 part 

 of slaked lime. This, when well mixed and reduced to one mass 

 of cement with the necessary quantity of water, is put into the 

 crevices or openings of the stone and the iron, both being previ- 

 ously damped, and after 48 hours the iron will be found thor- 

 oughly and lastingly fastened in the stone. 



EANSOME'S ARTIFICIAL STONE. 



The process by which this durable and ornamental stone is 

 made is exceedingly simple. Mr. Ransome, finding that the best 

 sandstones were held together by silicate of lime, after repeated 

 experiments made the unexpected chemical discovery that flints, 

 when boiled in a caustic solution of soda, under pressure, will 

 melt almost like tallow before the fire. With silicate of soda as a 

 liquid, he mixed chloride of calcium in solution, and produced 



