194 



SCIENCE 



[N. S. Vol. XXVI. No. 659 



chair to speak at large in the cause of sci- 

 ence, to insist upon the necessity for its 

 wider inclusion in the education of our 

 youth and the devotion of a larger meas- 

 ure of the public funds in aid of scientific 

 research ; to point to the supreme value of 

 science as a means for the culture of those 

 faculties which in man promote that knowl- 

 edge which is power; and to show how de- 

 pendent is the progress of a nation upon its 

 scientific attainment. 



But in recent years these truths have 

 been prominently brought before the asso- 

 ciation from this chair ; they have been ex- 

 haustively demonstrated by Sir William 

 Huggins from the chair of the' Royal So- 

 ciety, and now a special guild^ exists for 

 their enforcement upon the mind of the 

 nation. 



These considerations appear to warrant 

 me in following the healthy custom of so 

 many previous presidents— viz., of con- 

 fining their remarks mainly to those de- 

 partments of science with which the labors 

 of their lives have been chiefly associated. 



THE SCIENCE OP MEASUREMENT 



Lord Kelvin in 1871 made a statement 

 from the presidential chair of the associa- 

 tion at Edinburgh as follows: 



Accurate and minute measurement seems to the 

 non-scientific imagination a less lofty and digni- 

 fied work than the looking for something new. 

 But nearly all the grandest discoveries of science 

 have been the reward of accurate measurement 

 and patient, long-continued labor in the minute 

 sifting of numerical results. 



Besides the instances quoted by Lord 

 Kelvin in support of that statement, we 

 have perhaps as remarkable and typical an 

 exemplification as any in Lord Rayleigh's 

 long-continued work on the density of 

 nitrogen which led him to the discovery of 

 argon. "We shall see presently that, true 

 as Lord Kelvin's words are in regard to 



= The British Science Guild. 



most fields of science, they are specially 

 applicable as a guide in astronomy. 



One of Clerk Maxwell's lectures in the 

 Natural Philosophy Class at Marischall 

 College, Aberdeen, when I was a student 

 under him there, in the year 1859, ran 

 somewhat as follows: 



A standard, as it is at present understood in 

 England, is not a real standard at all; it is a 

 rod of metal with lines ruled upon it to mark the 

 yard, and it is kept somewhere in the House of 

 Commons. If the House of Commons catches fire 

 there may be an end of your standard. A copy of 

 a standard can never be a real standard, because 

 all the work of human hands is liable to error. 

 Besides, will your so-called standard remain of a 

 constant length? It certainly will change by tem- 

 perature, it probably will change by age (that is, 

 by the rearrangement or settling down of its com- 

 ponent molecules ) , and I am not sure if it does 

 not change according to the azimuth in which it 

 is used. At all events, you must see that it is a 

 very impractical standard — impractical because, 

 if, for example, any one of you went to Mars or 

 Jupiter, and the people there asked you what was 

 your standard of measure, you could not tell them, 

 you could not reproduce it, and you would feel 

 very foolish. Whereas, if you told any capable 

 physicist in Mars or Jupiter that you used some 

 natural invariable standard, such as the wave- 

 length of the D-line of sodium vapor, he would be 

 able to reproduce your yard or your inch, pro- 

 vided that you could tell him how many of such 

 wave-lengths there were in your yard or your 

 inch, and your standard would be available any- 

 where in the universe where sodium is found. 



That was the whimsical way in which 

 Clerk Maxwell used to impress great prin- 

 ciples upon us. We all laughed before we 

 understood; then some of us understood 

 and remembered. 



Now the scientific world has practically 

 adopted Maxwell's form of natural stand- 

 ard. It is true that it names that standard 

 the meter; but that standard is not one 

 millionth of the earth's quadrant in length, 

 as it was intended to be; it is merely a 

 certain piece of metal approximately of 

 that leng-th. 



It is true that the length of that piece 



