ZOOLOGY AND BOTANYj MICEOSCOPY, ETC. 129 



two drilled holes and 6-8tlis in. from the edge of the base-plate, the 

 two others at 6-8ths in. from the opposite end and 5-16ths from the 

 sides ; the screws project through the top of the plate about 3-16ths 

 of an inch. This completes the base-plate. 



The top-plate consists of a stiff thin plate of brass, 2|- in. long 

 by 2^ in. wide, with a central aperture of |- in. countersunk or 

 bevelled on one side, which forms the upper surface; three holes 

 are drilled to permit the three screws to pass through, and if the 

 circular thermometer be preferred a portion of the edge is cut away, 

 haK-moon shape, to permit of easy reading of the small thermometer. 

 To the non-bevelled surface is cemented a thin circle 5-8ths in. wide ; 

 a plain ring of brass, which will drop easily into the middle of 

 the inner groove flush with its upper surface, is soldered on to the 

 under surface of the top-plate. This completes the top-plate, which 

 should be platinum blacked. 



In use the top-plate is turned over, under surface up. On the thin 

 cover is put the droplet, with the objects for study, and, if required, a 

 very thin, small circle of mica or thin cover-glass is placed carefully 

 upon it, which will adhere by capillary attraction. An indiarubber 

 flat band, with an aperture that will just pass over the brass ring 

 without undue stretching, is put on, the width of the band or a little 

 sheet of pure indiarubber extending to the side edges of the top-plate. 

 If the observation is likely to be carried on for any time, a little olive- 

 oil or glycerine, or even water, is placed in the narrow groove, into 

 which the ring fits easily. To the two tubes in the base-plate are 

 attached two narrow indiarubber tubes about 8 in. long, into the 

 opposite ends of which are fised two glass tubes, drawn out at the 

 free ends into almost capillary orifices. The cover ready prepared is 

 now put on the base-plate, the brass ring dipping into the fluid in the 

 inner groove forming an air-tight trap, the nuts are screwed on to the 

 three screws and pressure made on the top-plate, so as to render, by 

 means of the wide flat band of indiarubber, the whole water-tight. 

 A piece of thick grey or drab cloth, with a central aperture 3-4ths in. 

 or 1 in. in diameter punched out of the centre, is placed on the stage 

 of the Microscope, and on it is arranged the warm stage. A vessel 

 containing hot water is supported on a tripod at one side or in front 

 of the Microscope ; one of the tubes is put into it, reaching to the 

 bottom ; the end of the other tube is placed in the mouth and the 

 water sucked through, and is then turned down into a vessel to receive 

 the water that passes round the outer groove, the rate of discharge 

 being in relation to the length of the lower limb of the siphon and 

 the entering orifice for the flow of hot water, as in Professor E. H. 

 Bartley's plan.* To ensure the water flowing round the groove, it is 

 best to place a partition in the outer groove between the two drilled 

 holes for the brass tubes. The water in the vessel may be maintained 

 at any required heat up to the boiling-point by means of a lamp or 

 gas flame, but if kept steadily at 160° Fahr. the thermometer indicates 

 a temperature of about 92° Fahr. Should plenty of moisture be 



* See tliis Journal, i, (1881) p. 672. 

 Ser. 2.— Vol. III. K 



