544 APPENDIX I. 



Balances for analytical work, to carry 100-200 gr., and turn to ^ of a 

 mgr., are to be obtained of G. KERN, Ebingen (Wiirtemburg), and 

 P. BUNGE, Hamburg (Eilbeck). Price, 200-300 mks. 



Small water motors, to be connected up directly with the water supply, 

 and particularly suitable, e.g., for setting centrifugal apparatus in 

 motion, are to be obtained of F. A. HEKBERTZ, Cologne. 



Thermometers: GREINER and FRIEDRICHS, Stiitzerbach ; EPHRAIM GREINER, 

 Sttitzerbach ; KIRCHLER, Ilmenau ; HAAK, glass-blower, Jena ; and 

 GEISSLER NACHF. F. MULLER, Bonn. For exact work it is essential 

 to have the thermometer tested. A normal thermometer made by 

 HAAK, Jena, gave the following results: At C. 0-10, at 10 

 0-00,- at 20 +0-05, at 30 +0-05, at 40 0-00, at 5C+0-05. 

 The negative sign indicates that the corresponding value is to be 

 subtracted from that directly observed. The corrections are true on 

 the assumption that the thread of mercury is throughout its length 

 at the temperature to be determined. If a part of the thread 

 projects outside the space whose temperature is" to be ascertained, 

 an addition must be made to the temperature read off and corrected 

 from the table of errors. The correction may be calculated from 

 the following formula : 



n (tf) 



6500 



Where (n) is the length of the projecting part of the mercurial 

 thread expressed in degrees, (t) the temperature to be measured, and 

 (') the mean temperature of the projecting thread. It is in most 

 cases sufficient to put for t' the temperature of the laboratory. If 

 this temperature is lower than the temperature to be measured, the 

 value found must be added to the temperature indicated by the 

 thermometer. 



Evaporating apparatus, apparatus for the distillation of water and for 

 heating drying chambers, can be obtained in all sizes from Dr. 

 MUENCKE, Berlin. 



Koch's steam sterilising apparatus, made entirely of copper, and 1 metre 

 in height, is to be obtained from H. B.OHRBECK, Berlin, N.W., Karl- 

 strasse 24, for 60-80 mks. See price list of 1891-2, p. 21. Particulars 

 as to the construction and manipulation of the apparatus are given 

 in the catalogue. 



Microscopes of excellent quality are to be obtained of C. ZEISS, Jena, and 

 of W. and H. SEIBERT, Wetzlar. A Zeiss microscope quite sufficient 

 for ordinary purposes is the following : Stand No. Vila, with eye- 

 pieces 2, 4, and 5, and objectives B and D. Price 153 mks. Mag- 

 nification 95-580. Drawing prism, 20-30 mks. ; the new drawing 

 apparatus of Abbe, which permits drawing upon a horizontal 

 surface, 60 mks. ; objective micrometer, 10 mks. 



A very satisfactory centrifugal apparatus, made after my designs (see 

 Fig. 155), is to be obtained, at a price of 60 mks., from G. TEGTMEYER, 

 mechanician at the Physical Institute, Jena. G. TEGTMEYER also 

 supplies my apparatus for determining the extensibility, elasticity, 

 and rigidity of plant structures, price 35 mks (see Fig. 179), as also 

 the apparatus devised by me and depicted in Fig. 49 and Fig. 146. 



