96 ARRANGEMENT OF APPARATUS, ETC. 



The only serious objections to the use of Swan's 

 lamp for Micro-photography, is the care and atten- 

 tion required when the electrical supply is produced 

 by a battery. The enormous expense entailed by 

 the purchase and working of electro-moters, placing 

 them beyond the reach of private individuals, in 

 fact, until electricity is supplied by accumulators or 

 from a central station parafin will be found far 

 superior. 



The actinic power of the electric light is inferior 

 to the intensity of its illumination, allowance must 

 be made for this when judging of the time necessary 

 for correct exposure. 



Grove's or Bunsen's elements are the best form of 

 battery ; bichromate cells from their inconstancy be- 

 ing a continual source of trouble. 



The lamp should be covered and mounted in the 

 same way as the parafin lamp before described ; or 

 one may be substituted for the other, if a flat hook 

 capable of slipping into an arrangement on the 

 pinion block of the stand, is fastened to the up- 

 right back of both. 



Magnesium in the form of Solomon's lamp may 

 be employed with low powers, when it is necessary 

 to shorten the exposure; but with high powers want of 

 light when focussing is the difficulty to be contended 

 with. The costliness of magnesium renders its pro- 

 longed use inapplicable to this purpose. 



Lime light gives excellent results, but the danger 

 and trouble connected with its use, along with the 

 impossibility of moving it about and centering, pre- 

 vent its extensive employment. 



