APPARATUS AND MATERIALS. 33 



and round files of different sizes; a vice. A small chest of thoroughly 

 good tools, attachable as a closet to the wall, is very useful. 



Chapman air-pump, attachable to a water-tap (costs about $3.00). It 

 should be connected with a mercury manometer-tube to make the ex- 

 haust visible. A Boltwood water-blast is often useful. 



Balances. For heavier work the Springer torsion-balance, costing 

 about $14.00, is excellent ; for transpiration experiments a delicate spring- 

 balance is most convenient, for which the Mail and Express Balance 

 (Pelouze Scale Co., Chicago, $5.00) is excellent. For a very accurate 

 balance carrying heavy weights, the balance 3423 of Gerhardt, 115 marks, 

 is to be recommended (see also page 79). For weighing chemicals 

 the Troemer balance, costing about $7.00, is ample for most purposes and 

 very convenient. 



Metronome. Costs about $4.00. 



Thermograph. Costs about $35.00, made by Richard Freres of Paris. 

 Hygrograph, or registering hygrometer. Costs about $35.00, made by 

 Richard Freres of Paris. 



Some form of sunshine-recorder is useful but not indispensable. 

 Photographic outfit. The camera should have a bellows long enough 

 to allow the photographing of small objects at least their full size, and 

 should take at least 5x8 plates. 



Spectroscope. May usually be borrowed from the department of 

 physics. A microspectroscope may be used, but the Kirchoff and Bun- 

 sen, costing about $30.00, is excellent and ample for this work; or the 

 Hoffman form, made by Max Kohl at 260 marks, is said to be excellent. 

 It must have a comparison prism (see Fig. 17). 



Polariscope. Not much used, and not indispensable : used on the mi- 

 croscope only. The Zeiss polarizer and analyzer, listed at 39 marks, is 

 ample. 



A simple steam sterilizer. The Arnold form is not expensive and 

 extremely good ; one of the larger sizes is needed. 



Measuring-glasses (graduates), cylindrical, preferably of 10, 100, and 

 500 cc. 



Four funnels of different sizes, about 20, 13, 8, and 5 cm. 

 Receptacles for, respectively, molasses, nutrient solution, lime water, 

 distilled water, alcohol. Aspirator bottles with ground-glass stop-cock 

 outlets at bottom are very good; for the two former liquids they should 

 be of a half-gallon capacity, for the three latter of a gallon capacity. The 

 mercury bottle may best be a "separating-funnel " which should be placed 

 over a tight wooden box to catch leakage (see Fig. 7). 



Three dry-battery cells, with tray or board to hold them, with a simple 

 circuit-closer. 



Oil or whetstone ; an emery wheel attached to a water-motor is very 

 useful. 



Simple still for distilling water. 



