ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



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in one piece with the disc a is of such a size that the rod g, fig. 65, fits 

 in it by means of the spiral /, and by this rod the chamber is heated.* 



Fig. 64. 



Fig. 65. 



Mr. J. S. B. Bell also recently suggested | a modified arrangement for 

 maintaining the preparation at any temperature from that of the room up 

 to 100°. It consists (fig. 66) of a mahogany slide 3 X IJ X 1/4 in., with a 

 flat groove 1/16 in. deep for the ordinary glass slide to lie in. In the 



Fig. 66. 



centre is a round hole 1 in. in diameter, which incloses a copper ring, 

 made by bending No. 16 wire into a ring slightly less than the hole. The 

 two ends pass longitudinally through the stage and are twisted together 

 and curled round. The stage is heated by a spirit-lamp held to the 

 twisted wire, and when the required temperature is reached the lamp is 

 moved back along the wire to a point that will just maintain the 

 temperature. At the time the stage was exhibited, the room was 62° F. ; 

 the slide was heated to 82°, and the temperature kept stationary. It was 

 then heated to 100°, and kept stationary for half an hour. In this 

 arrangement the heated wire is isolated from the stage and from the glass 

 slide by means of the wood in which it is placed, 



Mr. W. H. Symons' first form of stage | for steam, water, a saturated 



* Dr. C. H. Golding-Bird in 1875 suggested (Quart. Journ. Micr. Sci., xv., 1875, 

 pp. 373-4) a " diflferential " warm stage made with copper and iron wire, and intended 

 to correct the error which he considered the preceding forms of stage to give rise to, by- 

 reason of the difference of temperature between the copper and the centre of the glass 

 slide. 



t Micr. News, iv. (1884) pp. 19-20 ; and cf. Queen's Micr. Bulletin, ii. (1885) p. 4, 

 and iii. (1886) p. 13 (1 fig.). 



X See this Journal, 1882 p. 21. 



