366 Mr. Brooke on Nuttallite. [May, 



jet is about three-quarters of an inch, and a small wax taper is 

 fixed about half an inch beyond the platina. 



The only precautions I have found necessary are, to replace 

 the cap immediately after each experiment, and to employ a 

 pressure upon the hydrogen of not less than five or six inches of 

 water. With a pressure of nine inches I have never failed in 

 producing the same effect from platina foil of -g-^- inch in 

 thickness, by using the precaution of keeping it in a closed 

 tube ; but when the thickness of the platina foil was -s-jVo* **• 

 required to be previously raised to nearly a red heat. 



The experiment of the aphlogistic lamp may be exhibited to 

 great advantage by employing either precipitated platina or 

 platina foil suspended over the wick, instead of wire, as origi- 

 nally proposed. I am, dear Sir, truly yours, 



J. Cumming. 



P. S. By the kindness of our late Woodwardian Professor, 

 Mr. Hailstone, I have been favoured with some fragments of 

 titanium formed in iron slag, for the purpose of ascertaining its 

 place in the thermoelectric series ; which I find to be between 

 platina and silver, but have not as yet been able to determine 

 its precise situation with respect to the intermediate metals. 



Article X. 



On the Nuttallite, a new Mineral from Bolton, in Massachusetts. 

 By H. J. Brooke, Esq. FRS. &c. 



(To the Editor of the Annals of Philosophy.) 



DEAR SIR, April 20, 1824. 



I have received from my friend Mr. Heuland a small specimen 

 of a mineral from Bolton, in Massachusetts, brought by Mr. 

 Nuttall to this country. 



It had been named elaeolite, I suppose from its exhibiting a 

 play of light resembling that which is frequently seen in the 

 fettstein from Norway, and from its colour generally approaching 

 to that of the same mineral ; some fragments are, however, 

 nearly transparent and colourless. On examining the crystals, 

 which are imbedded in carbonate of lime, I find that they differ 

 both in cleavage and lustre from elaeolite, and that they are 

 much softer. They present the form of a right square prism 

 which may be regarded as the primary, with cleavages parallel 

 to its lateral planes. The lateral edges of this prism are replaced 

 by single planes, but the terminal planes are imperfect. 



It is softer and much more glassy in its fracture than scapolite, 



