108 
ORIGINAL COMMUNICATIONS. 
but both Pallas and Rehman have ascertained that the 
greater portion, if not the whole of this, is obtained in April 
and May, from the clefts of rocks in high and arid mountains 
surrounding lake Kokonoe." 
From the distribution of rhubarb in the Himalayas, Mr. 
Royle seems to think that it would be a profitable under- 
taking to introduce the true plant within the British Indian 
possessions; as for instance, in Kanawur or the Bhoteah per- 
gunnahs of Kemaon, where the soil and climate would be 
favorable to it, thus avoiding the immense distance that it has 
now to be carried. The species growing in the Himalayas, 
are the Rheum ribes (ribas of the Persians,) R, Moorcroftia- 
num, R. Ernodi, and R. spiciforme. The only difficulty in 
the way of the enterprise proposed by Mr. Royle, is that of 
obtaining either seeds or roots. 
J. C. 
ART. XXIII. — NOTICE OF THE OBSERVATIONS OF BERZE- 
LIUS, L. THOMPSON, AND M. VOGEL DE MUNICH UPON 
THE PROCESS OF JAMES MARSH FOR THE DETECTION 
OF ARSENIC. 
We again call the attention of our readers to the process of 
James Marsh for the detection of arsenic, for the purpose of 
recording additional information, and to point out other sources 
of error, and the means by which they may be avoided. Ber- 
zelius, in some observations upon several modes of detecting 
arsenic, [Journal de Pharmacie,) after giving an outline of 
this process, proceeds to remark: "Marsh has contrived a 
very convenient apparatus for this purpose, but he has em- 
ployed the gas by no means well. In fact, he allows it to 
escape by a small opening, he inflames it, and then places in 
the flame a plate of glass, which becomes covered with me- 
tallic arsenic, or else he directs the flame into a narrow tube, 
