Influence of Condition on Vapour-pressure, 61 



crank is in the lower part of its course, the power would be 

 acting against the motion of the ship. It is perfectly obvious 

 that the true fulcrum (from a practical point of view) is at 

 the shaft, and the resistance in the water. If we choose to 

 treat the point of instantaneous rest as the fulcrum, we must 

 introduce complications which will only result in bringing us 

 back to the simple practical view. 



Another analogous case is that of a bicycle rider. I need 

 not dwell on this, as, mutatis mutandis, the same considera- 

 tions apply as in the case of the steamer. 



The true theory of the oar has been discussed recently in 

 an appendix to a pamphlet entitled Ausa Dynamica, published 

 under the pseudonym of "John 0' Toole "*. The author 

 remarks that " In certain emergencies it might be highly 

 desirable for the captain of a vessel to know that the ( power ' 

 of an ordinary oar-lever is at a mechanical disadvantage. If 

 he is unaware of this, or, still more, if he believes the opposite, 

 he may send out an insufficient boat-crew to tow his vessel 

 out of danger. It is highly probable," he adds, " that vessels 

 have been actually lost in this way." 



VIII. Influence of Change of Condition from the Liquid to the 

 Solid State on Vapour -pressure. By W. Ramsay, Ph.D., 

 and Sydney Young, D.Scf 



N Wiedemann's Annalen, vol. xxviii. p. 400, W. Fischer 

 has published a paper on the above subject. After stating, 

 in the course of a historical sketch, that no experimental 

 work with a view to decide whether the vapour-pressure of a 

 solid is identical with that of its liquid at the same tempera- 

 ture below the melting-point of the solid has been carried out 

 since Regnault's time, he corrects himself in a footnote in 

 which he refers to a paper published by us on this subject in 

 the Philosophical Transactions in 1884. He there states, 

 however, that he gained a prize through some work on the 

 vapour-pressures of water and of benzene in 1883. Now it is 

 generally understood that priority is determined, not by the 

 date at which work is done, but by the date of publication ; 

 and as Fischer's work was not made public until July 1886, 

 there can be no question of priority between us. But in the 

 short sentence on our work he commits a grave error in stating 



* Dublin : Hodges and Figgis. 



t Communicated by the Physical Society : read December 11, 1886. 



