On the Lorentz Transformation. 249 



then closing T 3 and opening T 2 a little, the nitrogen in G can 

 be sacked into P, where, in contact with the P 2 5 , it remains 

 stored in a dry and pure state, lo be drawn off at will by 

 opening T 3 . 



The reaction is quite controllable, and the volume of gas 

 liberated can be adjusted to a nicety by varying the quantity 

 of bromine water run into G or the strength of the solutions 

 employed. The apparatus is quite small and as convenient as 

 an electrolysis generator for oxygen or hydrogen, which can 

 permanently be sealed on to any vacuum or other apparatus. 

 The gas thus prepared has been speetroseopieally examined 

 for its purity, and the absence of even a trace of the hydrogen 

 lines shows the gas to be quite pure. 



The same apparatus can be employed for the preparation 

 of small quantities of carbon monoxide by the interaction of 

 formic acid (in the separating funnel) and concentrated 

 sulphuric acid as represented by the reaction : 



H 2 C0 2 + H 2 S0 4 — >(H 2 + H 2 S0 4 ) + CO f , 



as well as any other gases that can be similarly liberated 

 under interaction of two such liquids. 



Christ's College, 

 Cambridge. 



• XXIX. The Lorentz Transformation. By L. A. Pars *. 

 TN obtaining the transformation of Lorentz 

 r {v 1 — \{u)(x —ut) 



I I r N / UX \ 



\0)=/i-^ 



by Einstein's method we make use of the condition that 

 there exists a velocity c invariant for the two systems of 

 space-time measurement. The object of the present paper 

 is to show that there is no need to make this assumption : in 

 fact, the existence of an invariant velocity follows from the 

 mere hypothesis of relativity. Granted only this hypothesis 

 the transformation follows; it is altogether more deep-seated 

 in the scheme of things than the consequent phenomena of 

 the FitzGerald contraction and the invariant velocity. Its 



* Communicated by Prof. A. S. Eddington. 

 Phil. Mag. S. 6. Vol. 42. No. 248. Aug. 1921. S 



