196 Mascellanies. 
itin an account of an examination, of another arsenical compound, 
which has been the subject of many experiments. It is the arseni- 
uret of iron with sulphuret of cobalt, described by Prof. Dana, an 
which you noticed in your late work.* I was engaged in the exam- 
ination, so long ago, as when its containing cobalt was the subject of 
your correspondence with him, and it has been occasionally the sub- 
ject of experiment since. It is a refractory compound, and while a 
pupil with Prof. D. 1 subjected it to all the processes which had been 
published, with a determination to finish its examination. Finding 
the characters of the constituent metals erroneously described, @ 
partial examination of them became necessary 3 want of sufficient 
leisure afterwards, prevented my completing what was begun. Some 
months since I prevented a friend from publishing his opinion, thatit 
contained no cobalt, by actual experiment. Prof. D. was however 
led into an error, in relation to the quantity of cobalt which can be 
detected by the blowpipe, from his trusting to the purity of a speci- 
men from Frederick Accum; it was merely a fused ore of cobalt: 
a ten thousandth of cobalt, can be detected by a practised eye. 
The value of the blowpipe as an instrument of research, has not 
been duly appreciated in this country ; few I believe use it with skill, 
even in mineralogical inquiries. 
9. Manufacture of lead pots, §c. by Messrs. Dixon.—We have 
pleasure in stating to the public, that there has lately been establish- 
ed in Salem, Massachusetts, a Manufactory of black lead pots; by ® 
process, the discovery of Messrs. J. and F. Dixon. These pots, ® 
we learn from the artists who have used them, prove on trial to pos- 
sess great advantages over other pots. Ist. They resist sudden change 
of temperature better. 2d. They are not liable to change their 
form, on pressure of the tongsina great heat. 3d. They are found 
to be far more durable. But their high estimation with those who 
have used them, is, perhaps, best proved by the fact, that the orders 
for them, have been so frequent, that the manufacturers have not bee™ 
and are hot now able to make them so fast as they are called for. 
Sees * % x % | * 
We are informed also that one of the Messrs. Dixon has ground 
and polished a concave fens for the venerable and ingenious Dr. ¥ 
ynde Oliver, of Salem, who has been constructing an achromauic 
WSS ee Seige Se 
* Elements of Chemistry, Vol. Uf, p. 200, 
