APPARATUS AND MATERIALS 



5* 



are at right angles to the support), permitting the whole arrangement to be 

 readily moved, though in fact it generally stands on one of the apparatus 

 tables in the laboratory. A great advantage of the saucer is that it saves 

 any spilled mercury, and would save all in the globe if this became broken, 

 or if the stop-cock were carelessly left open. At the same time the saucer 

 gives room for various accessories connected with the use of mercury, includ- 

 ing the bottle for used mercury, which should never be returned to the con- 

 tainer without cleaning. The saucer in the drawing is hollowed in the middle, 

 but saucers can be obtained with the middle raised, in which case an opening, 

 closed usually by a stopper, could be made at the lowest place near the mar- 

 gin, and thus the spilled mercury could readily be drawn off. A different 

 method of preserving mercury clean and ready for use is described by Arthur 

 in the Botanical Gazette, 22, 1896, 471. 



Pressure-testing Manometer. It is often necessary to test the tight- 

 ness of joints, stop-cocks, etc., to considerable gas-pressures, for which the 

 arrangement figured herewith (Fig. 10) serves admirably. To the upper 

 end of a piece of stout glass tubing, of about 

 5 mm. internal diameter and 75 cm. length, 

 there is attached, by stout rubber tubing, 

 a small funnel, while to its lower end there 

 is attached a stop-cock joint of the kind, 

 and bent to the form, shown by the figure. 

 The free end of this latter piece is provided 

 with a stout rubber tube into which may 

 te inserted, and wired, the tube or other 

 piece to be tested. When mercury is poured 

 into the funnel, any desired pressure up to 

 an atmosphere may be exerted upon the gas 

 in the piece under test. The stop-cock 

 permits this pressure to be released, and 

 allows the apparatus to be drained of 

 mercury, as may be desired. The whole 

 arrangement is tightly wired, with rubber 

 cushion pieces between, to a suitable board, 

 which may be kept hung up when not 

 needed, and may be stood in the mercury saucer, attached by clamps to the 

 upright rod, when in use. The instrument can also be used to give an 

 atmosphere of air-pressure for other purposes. 



Dryjng-oven. This is especially needed in the several studies where 

 it is necessary to secure dry weights of tissues. Many forms are obtainable 

 from dealers, one of the simplest and best of which is a double-walled copper 

 box, with water between the walls heated by gas below; it has a side door, 

 and openings in the top for exit of moisture, for thermometer, etc. I am now 

 using with much satisfaction a new oven, made by the International Instruct 

 ment Company of Cambridge, Mass., heated by the incandescent current 

 acting upon resistance plates at the back. It has the advantage that it gives 

 above 90 near the plates, and all gradations down to about 50° towards the 



Fig. 10. — Pressure - testing 

 manometer, with some 70 CM. 



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