ACCESSORY INSTRUMENTS. 



155 



the lamp repeatedly rinsed with warm water until it is suffi- 

 ciently clean, which is known by the water coming out quite 

 pure ; some boiling water may now be poured in and allowed 

 to remain for a few minutes to thoroughly warm every part ; 

 it must then be poured out, and the lamp turned upside down 

 and kept near a fire until it is dry, when it is fit for use again. 

 Care must, however, be taken not to allow the potash to run 

 over on the outside of any part of the lamp, as it wiU destroy 

 whatever bronze or paint it comes in contact with. 



When the lamp is required to be used immediately after 

 cleaning, turpentine or camphine may be employed with great 

 advantage : it readily dissolves the old oil, and even if a small 

 quantity has been left in, it wiU mix readily with new oil, and 

 aU the trouble of the potash and hot water will be avoided. 



Portable Candle Lamp. — Mr. Jackson, to whom we are in- 

 debted for so many improvements in the mechanical arrange- 

 ments of the microscope, employs as a substitute for a lamp a 

 candle lamp of the following construction: — a, fig. 108, repre- 

 sents a brass foot about three inches in 

 diameter, into which is screwed a tube, b, 

 about six inches long and one in diameter. 

 Within this slides a smaller tube, that is 

 provided with a cylinder of wax, which is 

 pressed on by a spiral spring, like a Pal- 

 mer's candle ; the upper part of this inner 

 tube is seen at d, it has fastened to it a disc 

 of brass, having a rim on its outer edge to 

 support the chimney, c, which is kept firmly 

 in its place by a thin circular ring of brass, 

 having three notches in its outer margin ; 

 these fit under three wedged-shaped pieces 

 of metal on the edge of the disc, and pre- 

 vent the chimney from falling off. The 

 cylinder of wax is not provided with a wick, 

 but a short piece of twisted cotton, to answer 

 the purpose of a wick, is placed upon a sharp point of wire, as 

 seen at e'. A condensing lens, /, provided with all the usual 

 movements for adjustment, can be attached to a small fin- 



Fig. 108. 



