262 Transactions of the [Sess. 



scope and a photographic camera. Another term, Micro-photog- 

 raphy, has a different meaning, and is applied to the production 

 of photographic pictures of large objects on a microscopic scale, — 

 email enough, in fact, to enable a microscopic object-glass of medium 

 power to see the whole of the picture in the field of the microscope 

 at one time. It is, however, only with Photo-micrography, the first 

 of the above terms, that I am to deal just now. 



Three things are essentially necessary to enable any one to 

 produce good Photo-micrographs. These are — (1) A competent 

 knowledge of photography ; (2) a considerable knowledge of micro- 

 scopic manipulation ; and (3) good apparatus, especially good 

 microscope object-glasses. As to the first of these, I have had an 

 experience of over a dozen years, more or less. As to the second, 

 I have had a large and varied experience with the microscope for 

 over thirty years, and during that period I have seen and handled 

 object-glasses by nearly every European maker of any note. As to 

 the third, I have at present a very excellent series of glasses, about 

 eighteen in number, extending from a four-inch up to Powell & 

 Lealand's famous water-immersion one-eighth. I merely mention 

 these facts to show that I am not a novice in the management of 

 the apparatus I am about to show you. 



In the production of Photo-micrographs, the first thing to do is 

 to have the camera and the microscope both firmly mounted on a 

 board. That now before you is about 3 feet 6 inches long, and 

 about 10 inches broad, by an inch thick to give it strength and 

 stability. It might with advantage be longer and a little broader. 

 The small camera, you will notice, is mounted at one end of the 

 board, on a platform raised about two inches above it. This is done 

 to cause the centre of the focusing screen of the camera to coincide 

 with the optical axis of the microscope when the latter is bent 

 back to allow its tube to enter the camera. The camera before you 

 is that known as quarter-plate size — that is, the size of the sensitive- 

 plate is 4| inches by 3j. This plate is generally large enough for 

 the purpose. If larger pictures than can be had in this way are 

 wanted, it is only necessary to have enlarged pictures printed 

 direct from negatives of that size. The camera has a pretty long 

 bellows, enabling it to be drawn out about 18 inches. The micro- 

 scope used is a plain one, with a very delicate fine adjustment, 

 and rack-and-pinion coarse adjustment. This latter is almost 

 an essential requisite in Photo-micrography, if ease and com- 

 fort in manipulation are desired. The microscope used has a 

 very large tube, more than \\ inch in diameter. This gives, 

 with the length of camera used, a large field, and enables the light 

 to fill the whole of the plate except the corners. The microscope 

 is connected with the camera by means of a conical hood of double 

 thickness of black calico, which is attached to the camera at the 



