( 541 ) 

 T A H 1> K VIII. 



iiecessiii'v tt) tak(> iiito acoonnl aii oleetroinagnetic stirrer, consistiii"- 

 of a soft iron i'o»l in ühis.s. in niy case it consisted of a cvliiidrical 

 portion with t^vo ItuIUs at citiiei' end. The bores were nieasnred 

 witli a micrometer screw, the length with a pair of sliding compasses. 

 Eacli time wiien tiie experimental tube had to be refilled with a new 

 qnantity of gas, it had to be opened at the top in oi-der to be 

 cleaned. Because the stirrer had to be brought in, it was not possible 

 to seal on a thin capillary as had been done for the manometer 

 tube. Noi- could the stirrer be placed into it beforehand, as this wouhl 

 be a hindrance in the cleaning and especially in the calibration with 

 mercury. The volume of the top portion was determined each time 

 after the measurements by cutting oif so much fi-oni the top tiiat (ui 

 that piece one division at least was well visible (the upper divisions 

 over a length of about 5 mm. were lost in the sealing). The fracture 

 was ground flat, the piece after being cleaned and dj'ied was ejitireh 

 tilled with mercury and the supertbu>us mercur\ was remoxed Uy 

 sliding a pro])erly cleaned Hat pieci? of glass over the gi-ound oil' 

 end. The mercury was weighed, the ])()sition of the ground end 

 was ol)Served with regard to the divisions of the tube with a cathe- 

 tomcter and from this the vohinie of the toj) ])ortion was derived. 



Physics. — '' fsothenna/s of /in'.rfurcs of oj'>/(/e/i. diid carhuii ditKvidi'. 

 II. llu' j)rejiaratioii of the iiu.iiiirt's and the com])r<'.-isil)irtiy 

 tit snidU di'ii.^iüi's." By W. H. Kkkso.m. Communication N". 88, 

 continued, from the Physical Laboratoj'v at Leiden, by Prof. 

 11. Kamkrijn(;h Onnks. 



((Communicated in the meeting of September :2(i, 1903). 



^1. In this [)ap(M' 1 shall describe the prcjKiralion of the mix- 

 tures of accurately known composition in the mixing apparatus 



