18 PRACTICAL PHOTO-MICROGRAPHY. 



weight of lead, jet he never attempts his most critical work 

 till after 9 p. M., though he does not live in a very busy thor- 

 oughfare but in a quiet suburb of London. The writer, too, 

 works in a cement-floored and walled half-basement in a very 

 quiet village, but has had negatives spoiled by the tremor of a 

 passing 'bus or of a heavy step overhead. There should be no 

 chance, therefore, of vibration or tremor in any part of the 

 apparatus or apartment. And further, the whole of the appar- 

 atus actually used to produce a negative the light, the con- 

 denser-system, the microscope, the camera and the plateholder 

 should all, during exposure at least, be practically one solid 

 mass ; in other words, the whole system must be firmly 

 clamped to one base, and that base should be the floor if pos- 

 sible. The entire system being clamped to one base, even 

 if that base be not itself above suspicion, moving, all 

 other parts move in unison, so that blurring may be 

 avoided ; we have heard of a plan by no means bad, 

 wherein the whole system on a strong base was suspended by 

 cords from a high support. If strong India-rubber formed part 

 of the length of these cords the apparatus was probably very 

 satisfactory, and the idea was surely ingenious. India-rubber 

 cubes have often been found very beneficial as supports for 

 the base-board of a system where tremor is inevitable. 



If by any chance the illuminant to be used is daylight, 

 whether diffused or direct sunlight, this consideration must 

 naturally play an important part in the selection of an apart- 

 ment. If daylight is to be used for the development of the 

 photographic plates, a course which we do not recommend, it 

 is almost essential that the window of the room chosen face 

 the North. The writer has but little experience of daylight 

 as the illuminant for making the exposure in the camera, but 

 where daylight, and especially sunlight, can be depended on, 

 it is perhaps the best of all illuminating agents. In Britain 

 we believe it impossible to obtain anything like uniform re- 

 sults, though no doubt at odd times great successes may be, 

 and have been, scored by sunlight. Now that photographic 

 emulsions are made so sensitive to actinic light, the great ad- 

 vantage of sunlight is of less consideration, while the superior 



