PHOTOMICROGRAPHY. Vins? 
PHOTOMICROGRAPH Y. 
{A communication to the Manchester Photographic Society.] 
By G. J. JOHNSON. 
HOTOMICROGRAPHY, or the process employed in photo- 
graphing the magnified images of microscopic objects, has 
been practised in France, Germany, England, and America for 
some years to a more or less limited degree, but of late has received 
a great impulse from the facilities afforded by rapid gelatine dry 
plates for the practice of the art by ordinary artificial light. Under 
the wet collodion system the sensitiveness of the film was too 
slight for practical use with the lamp or gas, and few cared to en- 
counter the somewhat precarious opportunity afforded in this 
climate by the happy conjunction of leisure and sunshine. ‘Too 
often has the writer been victimised when, counting on a morning’s 
holiday and having made all due preparation, the sun has uncere- 
moniously withdrawn his face just as the sensitised plate was placed 
in the camera, and for weeks together has refused to reappear at an 
opportune moment. 
The finest specimens of the art that I have seen were executed 
by Dr. Woodward, Surgeon-General of the United States Army, 
and residing at Washington, who has devoted much attention to 
the subject, and who evidently has been furnished by the Govern- 
ment with ample funds for carrying out his investigations. His 
apparatus is of the most complete description, an apartment being 
fitted up for the express purpose of taking photomicrographs, a 
heliostat provided, and lenses ground specially by Wales and others 
for accurate microscopic and photographic delineation. A report, 
fully illustrated, was published a few years ago by the American 
Government, containing the results of the labours of this scientist 
and his coadjutor, Dr. Curtis. Besides portraying such objects as 
diatoms, the nature of the delicate markings on which has been 
the subject of so much controversy in past years, these gentlemen 
have photographed numbers of pathological subjects, which, how- 
ever, present great difficulties to the photographer on account of 
the want of penetration in microscopic lenses. 
Mr. J. B. Dancer, the well-known Manchester optician, as long 
ago as 1840, produced photographs of microscopic objects, the 
image of a flea and other subjects being taken on silver plates. 
The first photographic illustrations of microscopic objects pub- 
lished in this country appeared in the Quarterly Journal of Micros- 
copic Science in 1853, Vol. I., since which period many works have 
been illustrated by means of these beautiful prints. 
Besides Dr. Woodward, the names of Drs. R. L. Maddox, Aber- 
