Scientific Intelligence — Geology, 429 



two diamonds, one of which weighs nearly a carat, and the other a 

 grain : both are crystallized in the form of perfect primitive octahe- 

 drons. M. Claussen was assured that all the diamonds which are 

 found in the itacolumite sandstone have rounded angles and edges, 

 whilst, on the contrary, those which are found in the psammite sand- 

 stone are perfect crystals. Were this fact verified, and found to bo 

 constant, we must needs suppose that the same cause which has changed 

 the sandstone into itacolumite has also operated upon the diamonds. 



The diamonds are never found enveloped in an earthy crust as 

 some authors have described. Their surface is sometimes rough, but 

 generally smooth. The diamond may very easily be recognised by 

 putting it in water, where it retains all its brilliancy, having the 

 appearance of a bubble of air, while all other precious stones lose this 

 singular appearance. 



It is quite incomprehensible how the Brazilian government has 

 not, up to the present moment, bestowed the slightest attention to 

 this highly important discovery. It would appear it has not appre- 

 ciated the importance of ever becoming positively acquainted with the 

 primitive or matter rock of the diamond, which, once known, might 

 lead to many discoveries as important as that of Santo- Antonio de 

 Grammagoa, and restore to a highly useful purpose the formerly 

 worked masses (cascalhos% by collecting and pounding all the pieces 

 of this rock which could be discovered. With this information it is 

 probable that in all time coming many more diamonds may be pro- 

 cured than formerly, which will of course greatly lessen their mer- 

 cantile value. — L'Institut, No. 379. 



6. Dartmoor granite as a building material, — Dr Buckland, at the 

 Plymouth meeting, exhibited a series of specimens from Lord Mor- 

 ley's granite quarries, in Prince Town, Dartmoor. To the depth of 

 fifty or sixty feet the granite is more or less decomposed, and it is sur- 

 face granite which has been employed in almost all cases, because it 

 was obtained cheapest ; and the result has been, that in all buildings 

 which have stood for any number of years, such as Dartmoor prison, 

 each block of granite has become a spongy mass, absorbing moisture 

 continually, rusting the iron bars employed in combination with it, and 

 rendering the cells so damp that they can only be used by covering 

 the walls within and without with Roman cement or tiles. This de- 

 fect is inseparable from all the granite which is not quarried from a 

 depth beyond the influence of decomposition. At the bottom of the 

 Morley works, a mass of granite is exposed to a great extent, and en- 

 tirely free from this influence ; it is from this the granite is obtained 

 now being used for Lord Nelson's monument in Trafalgar Square. 



VOL. XXXI. NO. LXri.— OCTOBER 1841, B 



