24 



Geologij of the Country 



[July 



site for the purposes of architecture, I think it one of the best materials 

 1 have ever seen or heard of ; perhaps equal, if not superior, to the 

 cement made with lime and puzzolana. 



For its analysis I must refer to Dr. MacLeod's report to Government, 

 which I am told contains the most accurate description of this magne- 

 site (a). 



After calcination it absorbs water with great avidity, and forms, even 

 by itself, a hard cement ; but, if mixed with a due proportion of sand, 

 it makes a marble-like cement, which, by what I have seen of the well- 

 conducted experiments and trials of Col. Monteith, is by far superior to 

 all those 1 have seen, Parker's not excepted. 



By the description we have of the magnesites found in various 

 parts of Europe, this of Salem differs from them all in its geological 

 position, and in its composition. 



As, among the European magnesites, there are some effervescing and 

 others plastic, probably none of them possessing both qualities at the 

 same time, Brongniart classed them under two species, the effervescing 

 and the plastic. This of Salem seems to differ, then, from them in this 

 respect, being both effervescing and plastic. 



It differs also in its gisement, since those near Madrid, Paris, Sali- 

 nelle, in Moravia, Piedmont, Elba, Silesia and Styria, are all imbedded in 

 rocks of secondary formation, and generally associated with limestones 

 and silicious minerals, such as chalcedony, chert, jasper, opal, &c. while 

 the Salem mineral contains none of these (a), and is imbedded in a pri- 

 mary stratified rock. The only magnesite which in Europe appears to 

 approach to the age of this of Salem, is that near Turin, which is imbed- 

 ded in serpentine. 



I am informed that in another locality, Yedichicolum near Trichino- 

 poly, close to the Cavery, there is another, and more extensive forma- 

 tion of magnesite, which contains, besides the minerals above enumer- 

 ated, chromate of iron ; I could not find a trace of this iron in the for- 

 mation of Salem (a), but it must be remembered that I only examined a 

 very small space of the large area that it occupies. 



This second formation of magnesite, besides the additional advan- 

 tage that could be obtained from the chromate of iron, and from the 

 circumstance of its being near a navigable river, has the quality of 

 being more easily calcined than this of Salem. 



The Shevaroy-hills, and those either near or connected with them, 

 are all of hornblende slate, and this formation seems to extend for some 

 miles west (No. 85). 



About five miles W. of Salem, in the nullahs, ravines and beds of 

 torrents, we see masses of gneiss (No. 86), which is the principal un- 



(a) See Note at the end of this Journal — Editor. 



