20 Transactions of the Society. 



effected by releasing the focal plane shutter in the reflex camera, 

 and its duration could be varied to suit the rapidity of movement 

 of the object, as in ordinary camera manipulation. In practice it 

 will rarely be found that high speeds are necessary. 



The only practical objection that I am able at present to see to 

 this method is that there is considerable liability of vibration on 

 the release of the shutter. In a camera such as I am showing this 

 evening (fig. 1), made by Messrs. Newman and Guardia, this 

 perhaps does not constitute such an objection, as they claim, and 

 I think with justice, that the exposure is effected so rapidly after 

 the release of the mirror that there is no time for the transmission 

 of a vibration to the apparatus itself. A much less expensive type 

 of camera would probably answer the purpose. 



I put this apparatus forward and make the suggestion in the 

 hope that it may be of service to some of those who wish for a 

 readily available means of obtaining a record of the appearance of 

 living micro-organisms under dark-ground or similar methods of 

 illumination. 





