672 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



the Microscope for an indefinite period and notes made of every 

 change occurring from day to day. 



A cell is built up to a suitable and convenient size of the strips 

 of thick plate glass, to be got from any glass merchant, then cement 

 a piece of the same plate glass in the centre of the cell with Canada 

 balsam and we have a watur-tight cell with a table of plate glass in 

 the centre, the space round which can be half filled up with water. 

 The object being placed on this table in water and covered with thin 

 glass, the water in the trough will hecp up any loss by evaporation 

 without any saturation of the table. It must necessarily be used 

 with the Microscope in a vertical j)ositiou. 



Wight's Growing-slide.* — Mr. W. H. Wight, of Baltimore, 

 finding the supply of water in the older forms of growing-slide to be 

 too limited and too soon exhausted, describes and recommends -the 

 following : — 



A small hole is drilled near the margin of a concave slide, or near 

 the centre of a plane one. Through this hole put a strand of cotton 

 thread with one end in contact with the glass cover, the other immersed 

 in a vessel containing the water, such as a soap dish, on which the 

 slides can be rested. Thus there is perfect circulation and a large 

 supply of water. The advantages of the j)lan are that it is inexpen- 

 sive and the glass slip can readily be used as an ordinary slide, besides 

 the opportunity always afforded of finding anything on the slide worth 

 future study, and of immediately converting it into a growing-slide, 

 thus avoiding the loss of rare objects. 



In a convenient resume of the growing-cells hitherto devised, f Dr. 

 A. C. Stokes, having had Mr. Wight's slide in constant use for a 

 month, finds it worthy of every consideration. A hole not more than 

 ^V inch in diameter, drilled by the sharpened shank of an old cataract- 

 needle and a piece of Clark's No. 70 sewing cotton doubled and loosely 

 twisted, have kept a deep cell abundantly supplied with water for 

 many days, a channel being cut in the ring for the thread and another 

 ojiposite to facilitate evaporation. 



Bartley's Warm-stage-l — Professor E. H. Hartley uses the appa- 

 ratus illustrated in the accompanying sketch, which is claimed to be 

 easy of construction, and to answer the purpose well. 



It consists of a vessel of water A, which is supported on a tripod 

 or a lamp-stand, and cajiable of being raised and lowered at will ; the 

 water in it is kept boiling when in use by the lamp C. A glass tube 

 a a, about 6 mm. in diameter, and about 30 cm. long, is bent upon 

 itself at g, so as to bring the two limbs parallel and within about 

 1 • 5 cm. of one another. One of the ends of this tube is then drawn 

 ofi" to a fine point, as shown at c, and is bent at an angle of 45° at a 

 distance of 3 cm. from this end. The other limb of this tube is con- 

 nected with the siphon tube d, by the rubber tube /. D is the stage 

 of the Microscope, and e e are two pieces of cork which serve as 



* Amer. Mon. Micr. Journ., ii. (1881) p. 23. 



t Amer. Jciurn. Miur., vi. (1881) pp. 50-8 (18 figs.). 



X Amer. Moii. Micr. Jouin., i. (1880) pp. 181-2. 



