890 



SCIENCE. 



[N. ri. Vol. XVH. No. 427. 



has finished posing the question? On the 

 contrary, I regard the names P. oceanea and 

 F. fasciata as equal in their pretensions, until 

 the choice is made. Once made, the person 

 that attempts to upset it is the true begetter 

 of confusion. 



But does Mr. Cockerell's conclusion follow 

 from his premises ? The conception under- 

 lying his application of the law of priority is 

 that place is to be reckoned as time. Now 

 a specific name has no standing until a de- 

 scription of the species denoted thereby has 

 been published, and until the name in ques- 

 tion has been associated therewith. Till then 

 it is a nomen nudum. The name Filistrata 

 oceanea is, we are told, a nomen nudum. 

 Even had it been published in a previous 

 paper, it would, in the absence of a descrip- 

 tion, have remained a nomen nudum. It ap- 

 pears first on page 50 of Mr. Banks' paper, 

 but without description; and it remains with- 

 out description for five whole pages. During 

 all this space, it remains a nom,en nudum. 

 Mr. Banks may asseverate as often as he 

 pleases that F. oceanea is identical with F. 

 fasciata. But F. fasciata does not exist (for 

 Mr. Cockerell), except as a nomen nudum, till 

 page 55 is reached. Here is a description at 

 last; but the name associated with that de- 

 scription is not F. oceanea but F. fasciata. 

 It is this latter then that ceases first to be a 

 nomen nudum. 



The case of Cucumiies lesquereuxii Knowl- 

 ton is different; but even this may, on Mr. 

 Cockerell's principles, be defended. For it 

 follows from the axiom 'places time' that 

 every name is a nomen nudum until the diag- 

 nosis or description is complete. But the 

 description of the fruit under discussion once 

 finished, Mr. Knowlton calls it, not Oucumites 

 glohulosus. but C. lesquereuxii. 



Mr. Cockerell may retort that this is mere 

 hair-splitting and childish chop-logic. It is. 

 But it is the natural outcome of an attempt 

 to subiect mere mode^ of expression to a rule 

 obviously intended to apply to essential mat- 

 ters and not to the niceties of style. 



To save all misunderstanding, let me repeat 

 emphatically that I am not defending either 

 Mr. Banks or Mr. Knowlton. I have no 



sympathy with people who print names for 

 the mere sake of rejecting them, or who tell 

 us what they might have done or what some- 

 body else might do if circumstances had been 

 different, and so forth. If such action be in 

 any degree checked by Mr. Cockerell's argu- 

 ments, their publication will have had one 

 good result. 



F. A. Bather. 



MOTION OF TRANSLATION OF A GAS IN A VACUUM. 

 (reply to MR. R. W. WOOD.) 



In the hope that if I bring around Mr. E. 

 W. Wood to my view of the energy required to 

 set a gas in motion of translation in a vacuum, 

 he will not find my explanation of the energy 

 changes which "take place when a gas expands 

 into a vacuum imnecessary, I will only take 

 up here that view. 



Mr. Wood in his second note (Science for 

 December 5) on a communication of mine to 

 the American Association says : 



We sometimes find the statement in text-books 

 that a gas expanding under such conditions that 

 no work is done experiences no cooling, for ex- 

 ample, when expanding into an infinite vacuum. 

 It appears questionable, however, whether a gas 

 can expand without doing work. Leaving out of 

 consideration the Internal work, i. e., the over- 

 coming of the forces of cohesion, we still have 

 the gas in the receiver doing work in giving a 

 motion of translation to the mass of gas thrown 

 out into the vacuum. 



I think, however, that it can be proved that 

 no work is necessary to set a gas in motion 

 of translation in a vacuum by the following 

 reasoning. Suppose that in a body of gas all 

 the molecules move with the same velocity in- 

 stead of having, as we assume according to 

 the kinetic theory, velocities varying greatly 

 in magnitude, and that the identical velocity 

 of all the molecules plays in other respects the 

 same part which we attribute to the mean 

 molecular velocity, e. g., that to each degree 

 of temperature of a gas a fixed velocity corre- 

 sponds, etc. Let that gas be compressed in a 

 receiver and then allowed to enter a vacuous 

 vessel which communicates with the latter. 

 What will happen ? To my mind, it can hardly 

 be conceived that anything else could take 

 place than the uniform distribution of the 



