1829.] 
Scientific Intelligence. 
379 
2d. Tourmalines which contain potash or soda, or both together, without lithia, and 
without a notable quantity of magnesia. The following are the varieties— I. Black 
Tourmaline from Bovey in Devonshire, found with quartz and phosphate of lime ; 
sp. gr. 3,246. II. Black Tourmaline from Eibenstock in Saxony ; sp, gr. 3,123. 
III. Green Tourmaline from Chesterfield, North America, sp. gr. 3,102. 
I. 
II. 
III. 
Boracic acid. 
4,11 
1,89 
3.88 
Silica, 
35,20 
33,05 
38,80 
Alumina, 
35 50 
38,23 
39.61 
Oxidulous oxide of iron, 
17,86 
7,43 
Protoxide of iron, 
23,86 
manganese. 
0,43* 
2,88 
Maa-nesia, 
o,70f 
Lime, 
0,55 
0,86 
Soda, 
2,00 
3,17 
4,95 
Loss in the fire. 
0,45 
0,78 
96,44 
101,51 
98,33 
* with magnesia, + with manganese, 
3d Tourmalines which contain a considerable quantity of magnesia. Four speci- 
mens were analyzed : I. Black Tourmaline from Kooringhricha, a province of 
Westmanland in Sweden ; sp. gr. 3,011. II. Black Tourmaline from Rabinstein, 
n Bavaria; sp.gr. 3,113. III. Black Tourmaline from Greenland; sp. gr. 
3,062. IV. Deep brown Tourmaline, from the mica slate of St. Gothard. 
I. 
II. 
III, 
IV. 
Boracic acid. 
3,83 
4,02 
3 63 
4,18 
37,65 
35,48 
38,79 
37,81 
33,46 
34,75 
37,19 
31,61 
Magnesia, 
Oxidulous oxide of iron, 
10,98 
9,38 
4,68 
17,44 
5,86 
5,81 
5,99 
7,77 
Oxide of manganese, 
1,89 
trace. 
1,11 
Potash, 
J 0,48 
0,22 
1,20 
11,75 
3,13 
0,98 
0,25 
trace. 
Loss in the fire. 
0,03 
1,86 
0,24 
98,11 
100,49 
96,48 
90,89 
M. Gmelin is at a loss to what cause to attribute the deficiency in the last ana- 
lysis. He thinks the tourmaline from St. Gothard should be again examined, 
especially as the loss in Bucholz’s analysis is still greater. 
2 . Specific Gravities. 
A communication appears in the Philosophical Magazine, for June last, pointing 
out what has been long known to every one, who has had occasion to examine them, 
viz. the little dependence to be placed on the table of specific gravities by Hassen- 
frantz, given in Thomson's System of Chemistry. The writer also shows that 
Hassenfrantz was equally erroneous in his calculated specific gravities of vari- 
ous compounds, and gives the true results deduced from the correct formula 
(w -f w ) ss 
W s' "4“ w' & 
in which w, w are the combining weights and s s the specific gravities. It is to 
be remarked that, Hassenfrantz is not the only writer who! has made a mistake 
on this point. In Aikin’s valuable Dictionary (Art. Allov) the very same mistake 
is made, as shown by Dr. Ure, who points out the correct formula. 1 Ins, with the 
many other gross errors we find every day in books, otherwise ot the highest autho- 
rity, should teach tli e student to examine and try every thing before he give impli- 
cit credence to it, however high the name by which it may come recommended. 
From the comparisons made by the author of this paper.it appears that in every 
case the calculated specific gravities are below the true, thus indicating condensa- 
tion But we would remark, that no hast)' conclusion should be drawn on this 
