310 Scientific Intelligence. [April, 



V. Mosaic Pavement. By N. J. Larkin, Esq. 



Mr. Larkin, member of the Geological Society, is about to 

 publish " An Essay on a Species of Mosaic Pavement, formed 

 of right-angled Triangles of different Colours ; with the Method 

 of calculating the Number of their Combinations," illustrated by 

 a series of engravings . 



VI. Cobalt and Silve?- Mine. 



We are informed by Mr. Mawe that the machinery for working 

 the cobalt and silver mine on the west edge of Dartmoor is 

 just completed, and the workings will shortly assume a regular 

 form. The large black masses of arsenical cobalt, contrasted 

 with the white curls of capillary silver and crystallized sulphuret 

 of silver, which fill the cavities of the quartz gangue, form speci- 

 mens peculiarly interesting, and almost rival those from Mexico. 



VII. Action of the Oxy-hydrogen Blow-pipe on Silica. By 

 Joshua Mantell, Esq. 



(To Dr. Thomson.) 

 SIR, Lewes, Dec. 10, 1817. 



The brilliant results obtained by Dr. Clarke, by means of the 

 oxy-hydrogen blow-pipe, induced me and my friend Mr. Robert 

 Ashdowne to embrace the earliest opportunity of repeating his 

 experiments, before the Lewes Philosophical Society ; and it is no 

 small gratification to us, to add our humbie testimony in corro- 

 boration of the accuracy of his statements. 



Our first attempts to obtain silicium were unsuccessful; but 

 we have since ascertained, that the failure originated from the 

 substance having been exposed to a temperature so intense as 

 to reduce the metal as soon as it was formed, into a substance 

 of a greyish appearance. We have since obtained it with much 

 facility, by placing pure silex mixed with lamp oil, before the 

 ignited gaseous stream for afeiv seconds only, and have invaria- 

 bly found the metal dissipated, when the fusion has been longer 

 continued. The silicium was as readily produced when the silex 

 was placed on charcoal, as when exposed on a tobacco pipe. 



We have taken the liberty of enclosing a few grains of the 

 silicium obtained last evening : its appearance agrees in every 

 respect with Dr. Clarke's description ; it has now " a greater 

 degree of metallic lustre and whiteness than the purest silver." 

 We hope it will retain its brilliancy till you receive it. 



With the greatest respect, I have the honour to remain, Sir, 



Your very humble servant, 



Joshua Mantell. 



The specimen possessed the metallic lustre in great perfection 

 when I received it, and I doubt not will retain it for years. This 

 metallic substance, obtained by my Lewes correspondents, forms 



