February 8, 1895.] 



SCIENCE. 



155 



cable to phenomena wUerever the investi- 

 gator maj' be, the restrictions of terrestrial 

 attraction were easily removed. By the 

 introduction of the so-called absolute 

 systems of units, one form of which is known 

 as the C. G. S. system, a great step in ad- 

 vance was made. It is no exaggeration, in 

 fact, to assert that one proper!}' educated in 

 the mechanics of our day and planet would 

 be as well fitted to investigate mechanical 

 phenomena on the companion of Sirius, as 

 on our diminutive member of the solar 

 sj^stem. 



The rigorous definiteness of terminology, 

 and the application of the C. G. S. system 

 of units in mechanics, are humorously set 

 forth in a little poem published over the 

 signature ' dp dt ' about twenty y^sirs ago 

 in the joiu-nal A^afiire. It is now known to 

 have been written by Clerk-Maxwell. This 

 poem purports to give an account of certain 

 lectures on the C. G. S. system delivered to 

 women by one Professor Dr. Chrschtschono- 

 vitich. The author figures as one of the 

 auditors, and her lamentations and criti- 

 cism run as follows : 



Prim Doctor of Philosophy 



From academic Heidelberg! 

 Yonr sum of vital eiiergj' 



Is not the millionth of an erg. 

 Yotir liveliest motion might be reckoned 

 At one tenth-metre * in a second. 



" The air," you said, in language fine 

 Wliich scicntilic thought expresses — 



" The air ' ' ( which with a megadyne 

 On each s<juare (cntimetre presses) — 



The air, and I may add, the ocean, 



Are naught but molecides in motion." 



Atoms, yoti told me, were discrete. 

 Than you they could not be discreter, 



Wnio knows how many millions meet 

 Within a cubic millimetre; 



They cUush together as they tly. 

 But you ! you dare not tell me why. 



Then, when, in tuning my guitar. 

 The inten-als would not come right, 



One-tentb metre — 1 metre x lO"'". 



" Tliis string," you said, " is strained too far, 



'Tis forty dynes, at least, too tight." 

 And then you told me, a.s 1 sang, 

 AVhat over-tones were in my clang. 



You gabbled on, but cverj' phrase 



Was stiff with scientilic shoddy; 

 Tlie only song you deigned to praise 



Was "Gin a body meet a body;" 

 And even there, you .said, collision 

 Was not described with due precision. 



" In the invariable plane," 



You told me, " lay the impulsive couple;" 

 You seized raj' hand, you gave me pain. 



By torsion of a wrist too supple. 

 You told me what that v\Tench would do; 

 " 'Twould set me twisting round a .screw." 



Were every hair of every tress 



Which you, no doubt, imagine mine, 



Ih-awn towards you with its Itreaking stre.s.s, 

 A stress, Siiy, of a megadyne. 



That tension I would sooner suffer 



Than meet again with such a duffer! 



Our survey of the develoi)ment of me- 

 chanical science is thus brought down to 

 the present time. But no account of i)rog- 

 ress can be complete without some allusions 

 to the grand problems which are now occti- 

 pying the attention of mechanicians. It is 

 hardly necessary to say that these are the 

 problems presented by the phenomena of 

 heat, light, electricity, and magnetism, oi-, 

 in short, the phenomena of that unseen 

 medium we call the ether. Just as the 

 problems presented by the solar sj'stem were 

 the absorbing questions in mechanics at the 

 close of the ISth century, so are the prob- 

 lems presented by the ether the engrossing 

 questions at the close of the 10th century. 



In approaching this subject, whether for 

 the present purj)Ose of popular exposition, 

 or for the higher purpose of investigation, 

 one must confess to a difficulty, apparent at 

 least, which might be raised by any hard 

 headed reasoner. It might be asked, for 

 example, by what right we speak of the 

 ether as a medium, when nobody has ever 

 seen any such thing? May we not be 

 merely juggling with mathematical sj'mbols 



