MISCELLANY. 
85 
ground, varies from twelve to eighteen inches in diameter, and its height is 
from ten to twenty feet. The gum exudes spontaneously from the tree, 
and it does not appear usual on any occasion to make incisions in order to 
procure it. Two kinds weTe shown me; one of a dark crimson color, 
called moselle, is esteemed the best, and its price at Muscat, is from six to 
eight rupees, the Bengal seers. I was frequently assured, that not one- 
tenth of the quantity which might be procured was ever collected by the 
Bedowins. As with the aloes, this appears to be consequent on there be- 
ing no regular demand." — Ibid, T. R. B. 
Ointment for Itch. — Dr. De la Harpe, chief physician of the Hospital 
of Lausanne, gives in the Gazette Medicate de Paris (July, 1840,) the fol- 
lowing formula for an ointment which he says he has very successfully 
employed in the treatment of upwards of 400 patients. Flowers of sul- 
phur 16 parts, sulphate of zinc 2 parts, powder of white hellebore 4 parts, 
soft soap 31 parts, lard 62 parts. 
The mean duration of treatment with this ointment was in 1836 eigh- 
teen, in 1837 fifteen, in 1838 eleven, and in 1839 ten days. — Am. Journ. of 
Med. Scien. 
New Theory of the Galvanisation of Metals. By W. Schcenbein. — 
Iron, zinc, and copper, are oxidized in the air, in water, and in saline so- 
lutions, as well as when they are in contact with other metals, or at- 
tached to the poles of a galvanic pile, as when they are isolated. But if 
a current is established, however feeble, the metals which form or are con- 
nected with the negative pole which receives the hydrogen are not at- 
tached. It follows from this, that the protection of copper by iron, as in 
the experiments of Davy, is due to a chemical decomposition of the wa- 
ter which occurs, however feeble the chemical action. It results from my 
experiments : 
1st. That neither ordinary or voltaic electricity are capable of modify- 
ing the chemical properties of bodies, and consequently that the electro- 
chemical theory of Davy and of Berzelius cannot be admitted. 
2nd. That the modifications which occur in the chemical properties of 
certain bodies when they are under the influence of contact, are due to the 
production of some substance, and its deposition on these bodies by the 
action of the electric current. 
3d. That the surest manner of protecting certain oxidizable metals from 
the action of free oxygen dissolved in water, is to place them in a voltaic 
current composed of the metal in question and one that is more oxidizable, 
both being in an electrolytique liquid, such as water which contains hydrogen. 
Combinations of Ammonia with Metallic Oxides. — A series of these com- 
pounds has been described by M. O. Rammelsberg in the Ann. de Pog. t. 
