284 Correspondence. 



Extract of a Letter from Lieut. Ouchterlony, Madras Engineers. 



" The mineral you speak of, the magnesite, is very well known here, 

 and it adds another to the many proofs which could be adduced of the 

 exceedingly bad state in which all such matters of scientific and economic 

 inquiry rest in this part of the world, when an immediate channel for 

 the employment of a newly discovered production of the soil is not 

 at once hit upon. The person who first, I believe, drew attention to 

 the importance of the carbonate of magnesia of Salem, was Dr. McLeod, 

 of our medical establishment, who made various reports to Government 

 about its value in the formation of a hydraulic cement. They received 

 much attention at the time, and an honorary reward was, I believe, 

 made to Dr. McLeod; but lately the subject was dropped, until Colonel • 

 Paley's experiments at home drew attention to it, and if not now 

 actually under favourable consideration, I imagine it is not quite lost 

 sight of. 



" I took several cwt. of it to England in 1836, to try to introduce it 

 into the chemical manufacturing districts, but met with no encourage- 

 ment ; as Tenant's house at Glasgow shewed me, that they could deliver 

 rough magnesia, resulting from the decomposition of the enormous 

 quantities of magnesian limestone used in their chlorine works, at so 

 low a rate, as to throw Indian magnesia in those parts — Liverpool, 

 Manchester, and Glasgow, — quite out of the market. The mineral is 

 exceedingly compact and homogenous, and it is impossible to obtain the 

 " calcined magnesia" of commerce from it in a sufficiently impalpable 

 state of division by a simple process by fire : it must be treated in the 

 usual way with sulphuric acid, and the magnesia produced from the 

 sulphate. For your purpose, viz. that of making the " Epsom salts," 

 and also the calcined magnesia for medicinal purposes, it would of 

 course answer admirably, and as I have a quantity here just now, I will 

 send you up a cwt. or so to experiment upon. The principal locality 

 is Salem ; but it is also abundant in the Trichinoply, Coimbatore, and 

 the Mysore districts; its site being in many places near enough to 

 the banks of the Cauvery to allow of its being brought down with 

 the stream of that river to Porto Novo on the coast at a very low rate 

 indeed, not so much as 10 rupees per ton, I am satisfied, and probably 

 a great deal less. 



" Its geological position is interesting, and I should much like to have 

 an opportunity of tracing out its peculiarity and its connection with the 

 igneous rocks, with which it is invariably found associated : indeed, its 

 origin is most likely the same, though the hypothesis, that it may be 



