( 223 ) 



Tlie nietlKxl of adjustniont of Mr. Schalkwijk will prove very useful 

 in many other cases. 



Tlie illumination is obtainerl by means of incnndoscents lamps 

 •which are moved along at a suitable distance of the apparatus. 



In order to read the position of the mercury in the tube A or in 

 the small tube C, we can, if perfect precision is not necossary and we 

 therefore need not take the readings by means of a levelling teles- 

 cope, utilize indicators 6xed to pieces of tubing, which can be moved 

 to and fro round the glass tube. 



§ 6. Remnrls on the constructing of the manometer. The appa- 

 ratus is constructed by Mr. G. J. Flim chief of one of the instru- 

 mentmakers workshops of the laboratory, whose able help was of 

 great value. Although the single pieces of manometer-tubes are 

 very large the constructing and handling especially of the type 

 JB did not offer great difficulties. But it need hardly be men- 

 tioned that all the operations have to be done very carefully 

 and cautiously, if so complicated an apparatus as the manometer 

 is not to have any leak or other defect. To persons who want 

 to construct such an apparatus the following remarks mav be 

 useful. In order to make a tube of the typo 7? the separately blown 

 cylindrical vessels with short capillary tubes (about 15 c.M.) bent 

 in the proper form (comp. fig. 2) are put together with the other 

 parts either suspended from pulleys or phiced on stands, provided 

 with pioper india-rubber tubes in which we can blow, and sealed 

 together by means of the hand blow-pipe (fed by a water blow 

 pump). In this way tubes of any lengtii can be sealed together. As 

 the mauonietertubc of the type 13, consists principally of capillarv 

 tubes it forms a very elastic whole. It is mounted on a loose boanl 

 between cork by means of clamps, cleaned with boiling, and dried 

 with the same precautions as the glass used for the thermometer 

 describe.] in the Proceedings of Mai 30*1' '96, p. 40 'j. During the 

 boiling the tube with the auxiliary board are placed in a sloping po- 

 sition, entirely filled and with both branches plunged into small basins, 

 and heated by means of a BuNSEN-flame regularly over its whole 

 length. After the drying the ends are provided with the steel caps, 

 /', (prepared beforehand) to which the steel capillaries (treated as 

 the thermonieter capillaries comp. Proceedings May 30'!' '9G, p. 41)-') 

 ■with the overpipo H' have been fastened (fig. 4). The steelcapillary 

 (comp. Proceedings Dec. '94, p. 168)^) (long 35 cM.) has been 



') Comm. of the Pliys. Lab. at Leydeii IS'JG, u". 27 p. 8. 



2) Ibid. p. 9. 



') Coiimi. of tlie riiys. I-ab. at, Leydeii 1S'J4, u". 14 p. 8. 



