History of Chemical Discoveries. 315 
14. Globular or Oolitic Carbonate (f' Iron^ according to Ber- 
liner, Ann. des Mmes, consists of 
Carbonate of iron, 81.2 
Carbonate of magnesia, 5.8 
Water, - 2.0 
Clay, ^ - 1 1.0 
15. Euclase, according to Berzelius, Ann. de Chim. xi. p. SI 6. 
consists of 
^ Silica, 
43.22 
Alumine, 
30.55 
Glucine, 
21.78 
Oxide of Iron, 
2.22 
Oxide of Tin, 
0.70 
98.47 
16. Wavellite^ according to Berzelius and Fuchs, see 
Chim. xii. p. 16. consists of 
Berzelius, 
Fucks. 
' Silica, - - - 
35.35 
37.20 
Phosphoric Acid, 
33,40 
35.12 
Fluoric Acid, 
2.06 
... 
t^ime, . - - 
- 0.50 
••r 
Oxides of Iron and Manganese, 1.25 
... 
Water, - - - 
26.80 
28.00 
99,36 
100.32 
17. Lasionite has been found by M. Fuchs to have the same 
composition as Wavellite. 
X. On the existence of Cantharidin in the Lytta vittata, or 
Potato Fly. By J. F. Dana, M. D. 
A peculiar substance called Cantharidin was found by Ko- 
biquet in the Meloe vesicato7'ius^ and is supposed to be the pe- 
culiar matter which produces vesication. The power of blis- 
tering is known to belong in an eminent degree to the Lytta 
vittata^ or potato fly, so common in North America ; and some 
American physicians have supposed that its vesicatory powers^ 
are even greater than those of the Spanish fly. 
In order to ascertain if this fly contained cantharidiiiy Dr* 
Dana, digested 110 grains of the potato fly for several days, 
and, after a series of operations, he obtained a number of minute 
crystalline plates, which, when washed in alcohol, and dried,, 
were white and pearly. When placed on the tender skin be- 
tween the fingers, they soon excited itching,, and produced redv. 
