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and the Use of the Kinematograph. 
With the film kinematograph over- or under-exposure, or 
a photograph which has been spoilt by accidental movement, 
has only to be missed out when printing, or if necessary 
the next photograph can be printed twice. 
On the other hand this machine has great advantages. The 
developing of the whole series of 350 photographs only takes 
the same time as that required for developing any ordinary 
sensitive plate, and printing is also perfectly simple, as the 
negative is simply placed on a positive plate exposed for 
a definite number of seconds to the light of a lamp and then 
fixed. Any number of positives can thus be made by an 
ordinary photographer with a very small expenditure of time. 
The cost of producing each negative is 3s. 6d. and each 
positive costs the same amount, so that each subject taken 
costs js. 
My experiments with both kinematographs extend over 
more than a year, and I have only quite recently succeeded 
in producing fairly good results ; but I think that most of the 
principal practical difficulties are now surmounted, and that 
the machine is in a fit condition for experimental work. 
I have used it successfully for other subjects, such as climb- 
ing plants, to show the movements of the leaves of the sensitive 
plant. 
I believe these are the first kinematograph experiments 
under natural conditions, daylight being used and artificial 
light only resorted to at night. It was thus possible to leave 
the plant undisturbed throughout the time of observation. 
I am indebted to Miss M. Smith, of Kew, for kindly drawing 
two figures for me from photographs. 
I am making microscopical investigations of the parts 
of the plant connected with movement, which promise some 
interesting results, but have thought it better to defer this 
to another paper, which I hope to publish shortly in conjunc- 
tion with Miss Richards of the Royal Holloway College. 
3 G 
