1884.] 



MICEOSCOPICAL JOUEl!iAL. 



205 



one of the first uses he will make of 

 such a lamp will be to burn his 

 fingers on the chimney — a propensity, 

 however, which he will soon over- 

 come. 



Mr. Bulloch's new lamp is shown 

 in Fig. 27, and the first one made was 

 sent to us for examination 

 last month. Having used 

 it somewhat in practical 

 work, we can speak well 

 of its convenience and ef- 

 ficiency. It will be seen 

 that the reservoir and base 

 are similar to those of the 

 Beck lamp, but that the 

 burner, instead of being 

 on the middle on the res- 

 ervoir, is placed on one 

 side. This gives room for 

 brass upright on the 



parts of brass. It is rather simpler 

 than Beck's. 



Not the least of the advantages of- 

 fered by these lamps is the opaque 

 chimney, which prevents any glare or 

 strain upon the eye, and confines the 

 light strictly to where it is desired. 



other side, which sup- 

 ports the bar carrying the 

 condenser. The latter is 

 focussed by sliding the bar 

 in either direction, and 

 the light is directed either 

 upward or downward by 

 swinging the arm as re- 

 quired, and clamping it in 

 any position by the milled 

 head shown. Only one 

 side of the chimney is 

 open, and the rectangular 

 aperture is covered with 

 a plane glass 3X1 slip, outside 

 of which may be slipped in a blue 

 slide or one with a ground surface 

 to modify the light. There is also 

 a brass slit, adjustable in width, 

 which fits outside of all. This is 

 intended to give a narrow line of 

 light. The chimney turns abovit the 

 bvu'ner, so that the broad face of the 

 flame or the edge can be used at 

 pleasure. 



The reservoir, carrying everything 

 upon it, moves up and down by a 

 rack and pinion on the upright bar 

 from the base, as clearly shown in the 

 cut. 



The lamp presents an attractive ap- 

 pearance, the chimney and reservoir 

 being nickel-plated and the other 



Fig 



h s New Lamp 



Maguifying Power. 



BY E. GUNDLACH. 



There is a general uncertainty as 

 to the magnifying power of an objec- 

 tive and the way it should be deter- 

 mined. 



A lens shows an object magnified 

 because it shortens the distance of 

 distinct vision, or rather the focal 

 length of the eye. The general mis- 

 take made in determining the magnify- 

 ing power of a lens is to simply di- 

 vide the focal length of the eye by the 

 focal length of the magnifier. If this 

 were the correct way, then, for in- 

 stance, a lens of ten inches focal 

 length would not magnify at all (the 



