THE POPULAR SCIENCE MONTHLY. 



W. A. Rogers, its builder, with which a 

 millionth of an inch can be easily meas- 

 ured, and with careful adjustment even 

 one twenty-millionth of an inch. In 

 principle the apparatus is an application 

 of Prof. A. A. Michelson's interferential 

 refractometer, the interference of light- 

 waves from mirrors attached to a 

 standard and to a compared metallic 

 bar enabling the observer to determine 

 minute movements with a precision 

 hitherto impossible. 



An inquiry into the properties of 

 paraldehyde and metaldehyde by Profs. 

 W. E. Orndorff and John White illus- 

 trated the inferences whereby the chem- 

 ist is able to body forth the respective 

 positions in a molecule of the atoms 

 which compose it. In the Anthropo- 

 logical Section the songs of sequence of 

 the Navajoes were rendered by a phono- 

 graph, an instrument which promises to 

 be as indispensable as the camera to the 

 serious traveler. A discussion of the 

 most animated kind took place in this 

 section between Rev. G. F. Wright and 

 Mr. W J McGee on certain evidences 

 adduced by the former of preglacial 

 man, Mr. McGee maintaining that the 

 evidence was merely probable and not 

 conclusive. 



OUR NEW INDEX. 



HALF a century ago science was an 

 affair of a few individuals, and a labora- 

 tory of any kind was to most people 

 only a curiosity. The man who devot- 

 ed himself to the study of Nature was 

 looked upon as a visionary having nei- 

 ther place nor function among the con- 

 tributors to human welfare; scientific 

 methods in the arts were rarely heard 

 of; natural knowledge had no part or 

 place in education ; and, besides an oc- 

 casional learned treatise, two or three 

 technical periodicals met all the needs 

 of scientific publication. 



But all this has now been changed. 

 The last half of the nineteenth century 

 will long be memorable as the period 

 during which science achieved a promi- 



nent if not a leading place in nearly 

 every department of human activity. 

 The wonderful advance of discovery, 

 closely followed as it has been by 

 numerous practical applications, has 

 wrought a revolution in many fields, 

 until in the arts, in commerce, in edu- 

 cation, and even in the professions, 

 science may justly claim to exercise a 

 controlling influence. 



With all this there has come an enor- 

 mous increase in the volume of scientific 

 literature. Scores of scientific periodi- 

 cals are engaged in the work of dissemi- 

 nating the results of investigation and 

 books by the hundred are published 

 every year in which the methods and 

 conclusions of science are given more 

 permanent record. The accumulation of 

 material from this ceaseless and ever- 

 increasing activity is already so great 

 that ready means of access to it be- 

 comes an urgent need of the hour. 



But it is only with a subdivision of 

 this great body of knowledge that we 

 are here specially concerned. In the 

 early days of the scientific awakening 

 just alluded to, it was only natural that 

 the results obtained by workers in sci- 

 ence should for the most part remain 

 the possession of the student and in- 

 vestigator. That science, however, had 

 a message for the people was not long 

 in being perceived. Side by side with 

 its many important industrial applica- 

 tions there had grown up a vast body 

 of scientific knowledge only needing 

 suitable interpretation to make it avail- 

 able for the masses. Under the stimu- 

 lus supplied by a few enthusiastic public 

 teachers there gradually arose a demand 

 for this new kind of knowledge that 

 would brook no refusal. In obedience 

 to this desire of the public we have 

 seen issuing from the press during the 

 last twenty-five or thirty years a steadi- 

 ly growing stream of popular scientific 

 literature embodying the ablest thought 

 of the time, and much of it the direct 

 product of our most distinguished scien- 

 tific men. 



