302 J. J. Woodward on the Magnesium and 
with five hundred diameters. Other powers require propor- 
tionate exposures, 
€ magnesium lamp used by me for this purpose was the 
of the mus he chimney and bag are furnished by the com- 
pany for $2.50. 
commenting on the above processes it may be remarked 
also the most difficult test 
objects can be satisfactorily reproduced. Where economy 0 
apparatus is the object, the magnesium lamp will be pe 
i one, the 
gsougie Hers who may be employed for work of this ¢ 
d the following remarks on the chemical process em- 
ployed in the production of the negatives from which the 
appended prints were made ammonium and potassium 
. 
. aa 
portrait collodion, rich in alcohol, 
a half, from the 6th square of a Méller’s diatom type-plate, spe 
cially prepared for the Army Medical Museum bv that skillful 
croscop! Th 
microscopist. e first from Negative 79 (new series), was t@- 
ken By. sunlight, with 40 diameters; in the second, from Nega- 
tive 123 (new series), the magnesium light was used, and every 
_ Ming else ‘remaining ne same, the distance was inc so as 
e 48 diameters; in the third, Negative 158 (new series), 
ectric lamp was employed, and every thing else still re 
