1836.] Scientific Notices— Mineralogy . 391 



sition, no elastic fluid is either absorbed or disengaged. To 

 ascertain the proportion of formic acid which is set at hberty 

 during the decomposition of a given quantity of the ether, tour 

 erains (previously rectified by distillation of chloride of calcium) 

 were let up into a solution of bicarbonate of potash standing in a 

 glass tube over mercury. The disengagement of gas commenced 

 after a few minutes, and lasted for about three days : it was 

 most copious when the light of the sun was strongest. 1 he 

 gas evolved measured 3-893 (German) cubic inches, = 2-1 U.J 

 Irains. This is equivalent to 1-768 gr. of formic acid. JNow 

 the atomic weight of formic acid is 37, and that of alcohol is 

 46: and 1-768 : 2-232 (4 - 1-768) :: 37 :46-8. Consequently 

 formic ether may be regarded as constituted of an atom ot 

 formic acid in combination with an atom of alcohol. 



Formic ether does not become acid in alcohol slightly diluted 

 with water, and behaves, therefore, in an analogous manner 

 with many of the compounds of chlorine with the acid metals 

 (tellurium, arsenic, antimony, &c.) which are dissolved by alco- 

 hol without undergoing any alteration, but are decomposed into 

 muriatic acid and metallic oxides when mixed with water.— 



(Ibid.) 



Mineralogy. 



4. Table of the Specific Gravities of several Minerals, 



The specific gravities of the following substances, which are 

 disposed nearly in the order of the system of Prof. Mohs, were 

 taken by William Haidinger, Esq. FRSE. 

 Okder I. — Haloide. 



1. Gypsum, a perfectly white transparent crystal from ^ 



Oxford ... . -•'^1^ 



2. Anhydrite, a rectangular four-sided prisin, obtained by 



cleavage, grey, semitiansparent, from Hall, iyrol.. Z'fiJJ 



3. Alumsto^ne, the crystallised variety on the surface ex- ^ 



posed in the drusy cavities, from Tolfa -•0^4 



4. The compact part of the same specimens ^'O^i 



5. Kryolite, the white cleavable variety • • • • ^'^"J 



6. Apatite, massive, asparagus-green, transparent, irom ^ 



Salzburg /.*/'* i" n V* '"> oor 



7. Apatite, asparagus-green crystals, from Cabo de Uata. o zzo 



8. Fluor,combinations of the hexahedron and octahedron, 



dark violet blue from St. Gallen, Styria •^"i^^ 



9. Fluor, an octahedron obtained by cleavage, ot a green- ^ ■ 



ish blue colour, from the Hartz ■•'" W \" '^ 



10. Fluor,tvvin crystals, pale violet blue by reflected light, ^ 



yfillovvish white by transmitted light, Alston .... o-l// 

 U. Fluor, an octahedron obtained by cleavage, pale violet ^ 



blue, Alston '^"^'^ 



