ON Se 
ee ee 
a ee Ree Te Clk a eee ae ee a ee ee ee aa 
O. N. Rood on producing Stereographs n Hand. 
The undissolved mass is to be well washed with a saturated so- 
lution of chlorid of potassium which, for reasons hereafter to be 
mentioned, is preferable to salammoniac. In this manner nearly 
the whole of the iron and palladium may be removed, while any 
insoluble impurities contained in the ore remain with the mixed 
double chlorids. 
New York, Oct. 31st, 1860. 
(Zo be continued.) 
Art. VIIT—On a Method of Producing Stereographs by Hand ; 
by Oapren N. Roop, Prof. of Chemistry in Troy University. 
[ With a Stereoscopic diagram. ] 
Sir Davip BRewsTER in his Treatise on the Stereoscope, (Lon- 
don, 1856) page 135, after describing a method of projecting the 
picture seen by one eye, of a symmetrical, geometric solid, and 
of sourons by reflexion from a maror a drawing of its stereo- 
¢ companion, states: “ When the geometrical solids are not 
pneu! their dissimilar pictures must be taken photograph- 
ically, from models, in the same manner as the dissimilar pictures 
of other solids.’ 
Upon page 200 of the same work he states, that though A 
ratus may be photographed directly, yet that stereoscopic diagrams 
can only be executed by the use of models made of wire, which 
are to be photographed in the usual wa 
ee same author in the article Stereoscope, Encylopedia Britan- 
ol. 1859, p. 690, writes: “As no artist, however 
skillful, is capable of executing two genie of any individual 
object, or group of objects, as the ey are seen by each eye sepa- 
rately, the stereoscope was of little sa before the art of ho- 
tography enabled us to take such pictures with the most perfect 
accurac 
In addition to pea statements, which would seem to imply 
the impossibility of producing stereographs by hand, I have not 
been able to learn from scientific friends nor from professional 
photographers, that any process is uow in use to effect this end, 
except the laborious and imperfect one of geometrical . 
jection. 
_ Under these circumstances, 1 venture to describe a sim ple method 
of drawing pA SOETAD HE, which possibly may manele a dans in- 
ent. 
this depart 
hen we examine attentively a photographic stere 
with the aid of micrometrical measurements, and adopt. the 
hand picture as a standard o hie wW find nom the | ht f 
os 
