( 1^^ ) 



small irregular vibrations occurring in most electrocardiograms, where 

 they sometimes reach a height of* 0,'J to 0.5 mm. and more», hut 

 are sometimes entirely absent, as e.g. in N". 6 of Mr. An. 



These vibrations are not caused by tremors ol" llio lioor or oilier 

 irregularities which should be ascribed to an insutllicient lechniiiue 

 as is easily shown by the vibrationless normal curves at the end 

 of almost every series of' electrocardiograms. Hence they must be 

 caused by electromotive agents in the human body itself and the 

 question arises whether they find their origin in the action of the 

 heart or of other organs. We may expect that an investigation 

 undertaken with this object will give a definite answer to this question. 



Physics. — Dr. J. E. Verschaffelt. "Contri.butio)is to tlte hioiüledje 

 of VAN DER Waals' \p-surface. VII. The eqifrition of state and 

 the xp-surface in the immediate neighhourliood of the critical 

 state for hinary niivtnres with a small proportion of one of 

 the components.''' (part 4). Supplement N". 6 (continned) to 

 the Communications from the Physical Laboratory at Ley den 

 by Prof. Kamerlingh Onnes. 



(Communicated in the meeting of May 30, 1903). 



17. The a, ^-diagram. 



In the previous communications the different phenomena in the 

 neighbourhood of the critical point in substan''e^ willi small propor- 

 tions of one component have, according to our plan set forth at the 

 beginning, entirely been expressed by means of the « and |>* and 

 the co-efficients that can be derived from the general enq^irical reduced 

 equation of state. For shortness, and to avoid the constant repetition 

 of the same factors (comp. ^1) I have used till now, instead of the 

 differential quotients of the general empirical reduced equation of 

 state, the co-efficients h, where the ??i's (comp. form. 19) have been 

 expressed by means of « and ;?, but henceforth, as the numerical 

 values are more important I shall make use again of the differential 

 quotients of the reduced equation of state itself, used in equation (1). 

 It seemed important to me to completeh' determine by means of 

 the numerical values of a and ^ the different cases which, according 

 to the formulae found by Keesom (Comm. N". 75) and by me (loc. 

 cit.), may pi-esent themselves in the relative situation of the different 

 critical points. To illustrate this I intend to divide an «, i>'-(liagrain 

 into fields in which there is a definite relative situation, by means 



