A VERY awkward word is this, and one which somehow sticks in the throat of its user in a most disagreeable manner. Why not Micro-photography? Sad to say, the latter term has already been annexed by the authorities, to describe the tiny photographs of scenery or country life which we used to find in ivory pencils or paper knives bought at the seaside. The field of photo-micrography is a very wide one indeed, embracing the vast insect population of the world, not to speak of the cellular growth of the whole vegetable and animal creation, great and small, or that unknown world of protozoa and bacteria, with which we are acquainted only through the medium of the high-power microscope. It stands alone as the only method of recording observations made in the regions visible through the microscope, the work of the hand craftsman being quite worthless. We may divide this field into three sections: (1) Low-power photo-micrography, which is concerned with the photography of subjects needing only a magnification ranging from two to sixteen diameters; (2) medium-power work, in which the magnification rises from eighteen to about 500 diameters; (3) high-power or critical photomicrography embracing magnifications from 500 diameters onwards, and of course demanding most accurate instruments, combined with the highest skill and experience.

Low Power Micrographs

Although these include by no means the least interesting class of subjects, the apparatus required is very simple, in fact any kind of enlarging lantern can be adapted. A thin wood slide, the size of the ordinary dark slide or enlarging lantern slide, may have a circular hole cut in its centre, about 3/4 in. in diameter, and a beading glued above and below, of the proper size to take the usual glass microscope object slides. Focussing must be done with the usual ruled glass plate. This method will serve very well for the enlargement on to a quarter plate of any fairly transparent object, such as an ant, spider, caterpillar, or other winged insect.

Lady Bird (Seven Spot) X 36.

Lady Bird (Seven Spot) X 36.

Harold S. Cheavin, F.R.M.S.

A daylight enlarging camera is to be preferred to the enlarging lantern, in which the condenser is so near the object. And if the operator possesses a camera of the old-fashioned type, focussing backwards, i.e. in which the front is fixed, and the focussing screen travels towards the operator, a still more serviceable contrivance may be erected, and one which will serve for opaque objects to be photographed by reflected light, as well as those which, being transparent, are photographed by transmitted light.

Having a piece of wood of the same width as the camera and about four feet long, the camera must be clamped at one end. Remove the sliding front carrying the lens, and fit it to the front of a large oblong box of cardboard, of the same diameter as the camera front, and carefully blacked inside with Brunswick black. This cardboard box is open at the back, and has a cloth hood glued on it, which covers an inch or two of the bellows and is held in position by a rubber band in one of the folds. A piece of wood, glued to the front part of the cardboard box at the bottom, will make it correspond in height with the baseboard of the camera. This will form an extension to fit into the front of the camera; extensions properly made, with bellows fitting either in front or behind the camera, are now to be obtained from camera makers for a few shillings.

The object must be raised on a stand to the same height as the lens, and behind it is introduced either a magic lantern with its front lenses removed, or some kind of condenser and lamp. A piece of ground glass between the condenser and the object (provided it is out of focus, or the ground surface will enlarge and show a grained image on the plate) will diffuse illumination and improve results considerably. Great care must be taken that lens, object, and condenser are well in one central line.

For all microscopic work backed plates should be used, preferably isochromatic, but when the illuminant is either oil or incandescent gaslight we need not always employ the yellow screen. Development should be very fully carried out, glycin or pyro-caustic soda being very suitable developers. An under-developed photo-micrographic plate is utterly useless.

For the printing of photo-micrographs, smooth gaslight paper seems preferable to all other methods; the least satisfactory is P. O. P. gelatine, owing to the great loss of detail in toning and fixing. A glossy surface paper must be chosen. For lantern slides, gaslight plates are far the best, and, as few operators would attempt photo-micrographs of larger size than quarter plate, they can generally be made by contact.

Medium- And High-Power Work

The essential outfit consists of a long extension camera, a microscope with object glasses, etc., a good lamp, and last, but not least, a solid platform. Makeshift arrangements, in which the various instruments are brought into contact with piles of books on an ordinary table, only end in disappointment and loss of time. The foundation of all things should be a piece of well-planed board, about 4 ft. long, 12 in. wide, and 1 in. thick, at one end of which the camera will rest screwed to a box or block of wood, which will raise the centre of the focussing screen to the level of the tube of the microscope when in a horizontal position. During the last twenty years the evolution of the field camera has proceeded on lines which render it most unsuitable for use in connection with the microscope, while the older patterns lack the necessary extension. Unless the operator possesses unusual mechanical and inventive powers, he will find it the cheapest way in the long run to invest in a proper camera, constructed for the purposes of photo-micrography. Daylight enlarging cameras can generally be adapted, but are somewhat cumbrous, considering the small size of plate in use and the great additional length of baseboard entailed.

The Microscope

Any good microscope, with a joint to the body enabling it to be inclined to a horizontal position, may be employed, but for a home-made arrangement a solid stand is essential, perfectly firm in all positions, no matter to what angle the body tube may be inclined. Tube and substage should be fitted with standard thread and gauge of the Royal Microscopic Society, all good modern lenses being made with this standard thread. Cheap and old-fashioned instruments are not always corrected for chemical as well as visual focus. Perfect correction of chromatic and spherical aberration, as well as close definition, are indispensable. The tube must be lined with black velvet internally, or at least blacked throughout; otherwise, when photographing without the eyepiece, there will be reflections from the metal surface, causing bright spots in the centre of the focussing screen.