INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 



529 



D is tte cooling evaporator, constructed of thin bronzed copper, and 

 covered witli a lid of perforated copper. A layer of thick felt is placed 

 inside for saturation. This vessel, filled with water and placed over 

 the shade as soon as the lamp is lighted, at once prevents the radiation 

 of heat upon the observer's head, and its use, during a long evening, " pre- 

 vents an annoyance which has long been felt by every microscoijist." 

 The felt only requires reraoistening once in every five or six hours. If a 

 thermometer is placed say 8 inches from the lamp when it is first 

 lighted, and on a level icith the top of shade (which is the usual position 

 of an observer's head when using the Microscope), it will bo found 

 that after the lamp has been burning an hour, the thermometer will 

 only indicate a rise of three or four degrees, whereas with lamps 

 having a terra-cotta or metallic shade the temperature would be raised 

 from twelve to fifteen degrees. 



Fig. 50. 



Kir.. r>l. 



It is claimed for this lamp that, iiulopcndently of the cooling 

 arrangement, it fulfilrf all the conditions of the most approved lamps 

 hitherto constructed for Microscopic use, with the adtlition oi a moro 

 effective shado and retlcctor. In consequence of mon; perfect com- 

 bustion, resulting from the shape of the chimney and arrangement for 

 th(! ingress of air, an iibinidance of light is siq>plit!d for the higher 

 powers. 



