6 Wenham, on Microscopic Photography, 
It is most remarkable how an impression of the finest details 
of an object, or the markings on even the most difficult tests, 
may be obtained by means of the photographic microscope, 
and so definitely that I have used it for proving their struc- 
ture.* 
The application of photography to the delineation of 
microscopic objects is somewhat limited, not by any diffi- 
culties or defects in the process, but by occasional peculiarities 
of colour, or transparency in the objects themselves. Many 
insect, animal, and vegetable structures, though sufficiently 
transparent to the eye, are absolutely opaque to the actinic 
rays. I possess a specimen of a parasitic insect of a dark red 
tinge, and in which a splendid internal tracheal system can 
be discerned. I have tried every means of obtaining a pho- 
tographic representation of this, but without success. With 
all periods of exposure the object appears as a mere blank 
space, or like a hole cut in a sheet of paper. Until further 
discoveries have removed these difficulties, the application 
of microphotography must be to some extent restricted, as 
many objects are for this reason excluded. All structures 
dependent upon outline or opacity, such as sections of bone 
and wood, vegetable fibres, &c., may be delineated with ease 
and certainty. 
In conclusion, I will enumerate the peculiar advantages of 
my method ; first, the use of the ordinary microscope as a 
solar one, a dark room serving as a substitute for a camera ; 
the additional apparatus required will cost but a few shillings. 
Second, the method of obtaining the combination of the che- 
mical and visual foci, which I have found to be of great 
practical utility ; third, the mode of obscuring for a time the 
parts of the object either easily solarised and lost, or out of 
focus. I have not advanced these as mere speculations, but 
have submitted them successfully to the test of repeated trial. 
I may also remark that when sunlight is to be obtained, I 
have found the practice of microscopic photography to be one 
of particular certainty, for unlike other branches, the con- 
ditions of light are so favourable and definite, that an impres- 
sion may always be obtained ; and though the present state of 
the science in this department is admitted to be imperfect, 
yet there can be no question that it is still progressive, 
* Within the last few days I have succeeded in obtaining a photo- 
graphic impression of the P. angulatum, magnified about fifteen thousand 
diameters, showing the configuration of the markings perfectly black and 
distinct in a far greater degree than we can ever hope to see them through 
the compound microscope ; and it is my opinion, that if ever the structure 
of these difficult tests is to be proved it will be by the aid of photography. 
