198 ROCHESTER ACADEMY OF SCIENCE. | June 22, 
The following paper was accepted for publication by the Council : 
ON THE SEPARATION AND STUDY OF THE HEAVY 
ACCESSORIES OF ROCKS. 
By ORVILLE A. DERBY. 
The importance of the study of the accessory elements in rocks is 
universally recognized by petrographers, and various ingenious and 
useful methods have been devised for their isolation from the more 
abundant essential elements in the midst of which they usually play the 
part of the traditional needle in the haystack: The methods of separa- 
tion by treatment with acids, use of heavy liquids, and of the electro- 
magnet are essentially laboratory processes, and become expensive and 
tedious when any considerable amount of material is to be treated. 
The use of these methods could be greatly extended if the greater part 
of the essential elements could be got rid of by some rapid and inex- 
pensive process. The primitive panning process of the gold and 
diamond miner, which depends on the sorting power of water in motion 
in a suitably shaped vessel, is admirably adapted. for this preliminary 
concentration. 
Although the method of washing rock powder in water was 
employed with striking success by Cordier in the early part of this 
century, it seems to have been generally neglected until recently 
revived by Thurach in his admirable studies on zircon, etc. Without 
knowledge of the latter’s methods and results, the writer and his 
assistants have, during the last few years, employed quite extensively a 
process suggested by an experienced miner, which differs from that olf 
Cordier and Thurach in the use of the batéa or Brazilian miner’s pan 
instead of the glass or porcelain dishes of the laboratory. 
The batéa is a vessel of the shape of a conical kettle cover without 
the raised rim. ‘The best material is copper, as wood is cumbersome 
and is liable to retain fine mineral grains in its fibers and thus carry 
them over from one wash to another, while zinc, tin and iron are more 
subject to oxidation than copper, and the two latter do not permit the 
use of the magnet when it is desirable to remove magnetite in the 
course of washing. Any tinsmith can make the instrument. Tolerably 
thick sheet copper strengthened with a heavy wire set in the rim should 
be used, and the joint should be carefully smoothed so as to make the 
inner surface as regular as possible. A diameter of 12 inches, with an 
angle of 120° at the apex, gives a convenient size and shape, as it is of 
