APPARATUS AND MATERIALS 



49 



o 



accompanying figure (Fig. 8). If the filled upper bottle is allowed to siphon 

 through the rubber tube into the empty lower (the flow being regulated by 

 the interposed glass stop-cock, or else by a screw pinch-cock), the upper open 

 tube gives an aspirator or exhaust current, and the lower a blast or aerator 

 current. The bottles may very readily be transposed, — 

 by a pulley arrangement if desired. 



Blast. Needed for developing great heat in glass- 

 working, for aerating water-cultures, etc. For the former 

 a foot-bellows blast, sold by all supply companies, is 

 best, and for the latter, various forms of glass or of 

 metal, working by water-pressure, are offered by supply 

 companies, the Boltwood form being considered very 

 efficient. For most purposes an excellent blast is given 

 by the aspirator just described. A simple arrangement 

 for aerating solutions is described by S. O. Mast in 

 the American Naturalist, 38, 1904, 655. 



Balances. Of these it is best to have three or four 

 forms for the markedly different uses, and they should, 

 the best of them at least, be kept in a case, permitting 

 their use in position, attached to a solid wall of the 

 laboratory without connection with the jarring floor. My 

 own case is shown in the photograph of the laboratory 

 on Plate III. For weighing chemicals a Troemner 

 Balance (costing about $7.00) is very good, and should 

 be kept in the case for chemicals. A spring balance, 

 though too inaccurate for any scientific use, has many 

 conveniences for rapid weighing, and a good form is the 

 Mail and Express Balance of the Pelouze Scale Company 

 of Chicago (cost $5.00). For a large balance taking 

 heavy weights, and having long pan supports, the 

 Gerhardt 3423 (costing 115 marks) is excellent. The Fig."8. — Aspirator 

 Springer Torsion Balances, having the beams under the and aerator; XtV- 

 pans, are also good, though less delicate. For a sensitive Particulars in text, 

 large balance, which at the same time will take plants, 

 etc., of any height, my own transpiration balance among my normal appara- 

 tus (page 46) is very efficient. For precise work with very small quanti- 

 ties, as occurs frequently in quantitative studies, a good form, sensitive to 

 one-tenth of a milligram, is necessary, and excellent ones of this sort are sold 

 by all dealers. The weights of these accurate balances must be carefully 

 guarded against possible alteration through adherent grease, etc. 



Photographic Outfit. This is essential in any modem scientific lab- 

 oratory, but it differs so much with the taste and interests of the individual 

 that recommendations are needless. My own includes a King Camera, with 

 bellows extensible to permit photography of natural size, or even with a little 

 enlargement. It takes a 5x8 plate, has a Zeiss Anastigmat lers, and is 

 arranged on a solid tripod stand adjustable for height and angle. Directions 

 for laboratory photography may be found in the volumes of the Journal of 



