158 ILLUMINATIOX FOR THE MICROSCOPE. 



illumination is rarely called for, except as a means of control, and 

 subcritical or diffuse illumination, as obiained by racking the 

 condenser a little out of focus, is preferable and more commonly 

 employed. The lamp here described furnishes a light for ordinary 

 work, which, in many respects, is preferable to any I have hereto- 

 fore employed. 



While this fifteen-volt lamp can be readily maintained at full 

 incandescence by the current from an eight-cell storage-battery, 

 the care of this latter is by no means an insignificant matter ; and 

 I am not prepared to recommend its use unless one has access to 

 one of the street circuits. In this city we have at our disposal 

 either the Edison circuit, with a pressure of from one hundred and 

 ten to one hundred and twenty volts, or the alternating current, 

 distributed to houses under a pressure of fifty-five to sixty volts. 

 If the fifteen-volt lamp be connected directly with either of these 

 circuits, it would be instantly destroyed. It is necessary to 

 neutralise, or take up a portion of this pressure, by the introduc- 

 tion of a suitable resistance. This can be conveniently accom- 

 plished on the Edison circuit by the interposition of a one- 

 hundred candle power, one hundred volt, three ampere lamp of 

 the '•'• mu7iicipar^ type, the two lamps being connected in series. 

 Both lamps will, when thus arranged, burn at full incandescence ; 

 but, as we do not desire to employ the larger lamp, this may be 

 placed under the table and covered with a box. 



In photo-micrography the writer has made use of nearly all 

 the methods of artificial illumination that have been proposed, 

 including the electric arc, electric incandescent with coiled carbon 

 of one hundred candle power, calcium light, Welsbach gaslight, 

 and kerosene oil. The lamp here described he finds infinitely 

 more convenient and amply efficient. For the study of absorption 

 spectra by means of artificial light, this lamp gives an ideal 

 illumination. — New York Medical Journal. 



Dr. A. Famintzine has found some remarkable new forms of 

 bacteria in the aquarium of the Botanical Laboratory of the 

 Imperial Academy at St. Petersburg. 



