4(jt Astronomical Society. 



various analyses of minerals of the Tourmaline family which 

 have been made by former chemists. He then describes the 

 methods which he adopted in his own experiments, and adds 

 the results which he obtained from them. 



The author divides the different species of Tourmaline into 

 the following sections : 1st, Tourmalines which contain 

 lithion ; 2d, Tourmalines which contain potash or soda, or 

 both these alkalies together without lithion and without a con- 

 siderable quantity of magnesia ; 3rd, Tourmalines which con- 

 tain a considerable quantity of magnesia, together with some 

 potash, or potash and soda. 



" It appears," he says, in conclusion, " that when we com- 

 pare the analyses of the different species of Tourmalines, the 

 most essential ingredients are boracic acid, silica, and alu- 

 mine, whose relative quantities do not vary much. It appears 

 further, that any alkaline substance, though in no considerable 

 quantity? may be likewise an essential ingredient. The dif- 

 ferent nature of these alkaline substances may be employed 

 by the chemist, as we have used it, to divide these minerals 

 into different sections. But it will appear to be quite useless 

 to attempt to give mineralogical formulae for the chemical com- 

 position of these minerals, when it is considered; 1st, that we 

 can by no means rely upon the correctness of any statement 

 regarding the quantity of oxygen in boracic acid ; 2dly, that the 

 quantity of alkaline bases, whose oxygen would be unity, is so 

 small, that it cannot be determined (with sufficient accuracy) 

 without great errors in the computation of the relative quantity 

 of oxygen in the other ingredients ; 3dly, that in one species no 

 account could be given of a considerable loss of weight. He 

 has, however, calculated the quantities of oxygen in every 

 species, with the intention of comparing the sum of the oxy- 

 gen contained in the bases, with the sum of that contained in 

 the acids, viz. boracic acid and silica. The result of this cal- 

 culation is then fully stated. 



ASTRONOMICAL SOCIETY. 



Dec. 10. — At the meeting this evening, the publication of 

 the Second Part of the First Volume of the Memoirs of the 

 Society was announced, the contents of which will be found 

 in our " Notices respecting new Books." 



A paper, drawn up by Dr. Gregory, was read, containing 

 a Description of a Box of Rods, named the Rhabdological 

 Abacus, presented to the Society by the family of the late 

 Henry Goodwyn, Esq., of Blackheath. It appears that these 

 rods were invented by Mr. Goodwyn, for the purpose of fa- 

 cilitating the multiplication of long numbers of frequent oc- 

 currence ; 



