C o N T E N T S. XI 



NITRATION of symmetrical dinitroauisol. 650. 



NITROGEN (A bath of liquid) at ordinary and at reduced pressure, öol. 

 OBSERVATORY AT LEYDEN (Ou the yearly periodicity of the rates of the standurdclock 

 of the), Hohwii ii<\ 17. (I). 68. (11). 15)3. 



— (Preliminary investigation of the rate of the standardclock of the) Hohwii nO. 17, 

 after it was mounted in the niche of the great pier. 267. 



OSS (s. L. V A n). I ive rotations in -S^ in equilibrium. 362. 



PARALDEHYDE (Equilibria ot phases in the system : acetaldehyde -\-) with and without 

 molecular transformation. 283. 



PARALLELOTOPES (Relations between diagonals of). 540. 



PEKELHARING (c. A.) presents a paper of Prof. K. F. WeiNCKEbach : "On the 

 duration of the compensatory pause after stimulation of the auricle of the mam- 

 malian hea^t". 378. 



PENCILS (On the spheres of Monge belonging to ordinary and tangential) of qua- 

 dratic surfaces. 484. 



PERIODICITY (Ou the yearly) of the rates of the standardclock of the Observatory at 

 Leyden, Hohwii NTo 17. (I). 68. (II). 193. 



PHASE RULE (Galvanic cells and the). 182. 



PHASES (A representation in space of the regions in which the solid) which occur, 

 are the components, when not forming compounds. 279. 



— (Equilibria of) in the system ; acetaldehyde -|- paraldehyde with and without 

 molecular transformation . 283. 



PHENOMENA (Critical) in partially miscible liquids. 307. 



— (Critical) of partially miscible liquids-Ethane and Methylalcohol. 473. 



— (Some remarkable), concerning the electric circuit in electrolytes. 465. 

 Physics. J. D. VAN DER Waals: "'leruary Systems". (IV) 1. (V). 121. 



— J. D. VAN DER Waals Jr.: "Statistical electromechanics". (I). 22. (II). 114. 



— P. Zeeman: "Observations on the magnetic x-otation of the plane of polarisation 

 in the interior of an absorption band". 41. 



— W. H. Julius: "An hypothesis on the nature of solar prominence". 162. 



— A. H. SiRKs: "On the advantage of metal-etching by means of the electric 

 current". 219. 



— J. D. VAN DER Waais: "On the conditions for the occurrence of a minimum 

 critical temperature for a ternary system". 225. 



— W. H. Keesom: "Reduction of observation equations containing more than one 

 measured quantity". 236. 



— L. H. Siertsema: "Measurements on the magnetic rotation of the plane of pola- 

 risation in li([uefied gases under atmospheric pressure. II. Measurements with 

 Methyl.ihloride". 243. 



— H. Haga and C. H. Wind: "Diffraction of Eontgen-rays" (2nd communication). 

 247. 



— H. A. Lorentz: "The fundamental equations for electromagnetic phenomena ia 

 ponderable bodies, deduced from the theory of electrons". 254. 



