194 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1924 



thinking may be artificially done, but knowledge and understanding 

 must be actively sought and used. Man is the only animal that can 

 do this. 



Scientists know that research merely discloses new parts of the 

 infinite unknown. Paradoxically, the enticing, helpful " unknown " 

 increases as men continue to subtract from it. Progress in every line 

 of experimental science follows the same law. The apparently nar- 

 row path gradually expands into unlimited, unexplored territory. 

 AVith his new tools and his increased speed of communication man 

 finds that he can advance into the unknown faster than his ancestors 

 could, and children seem to learn more rapidly than he did when he 

 was young. The scientists of the twentieth century are legion. But 

 scientists were anathema a short time ago. There is to-day more 

 chemistry in the atom than there was in all " inorganic " chemistry 

 a few years ago. There is more in the " sugars " now than there was 

 in all "organic" when the writer studied it. There is more im- 

 mimity in blood and more heredity in the microscopic chromosome 

 than there was in all biologj' until recently. There is more crystal 

 structure research by X rays now than research in all mineralogy 

 when Agassiz came to America. 



In the preparation of an article the purpose of which is to direct 

 attention to the interest connected with research work in general 

 there is special reason for selecting as the subject such a narrow field 

 as the vacuum. The writer wishes to show that in a vacuum, of 

 which one might say "There is nothing in it" (and surely less than 

 in anything else), there is, indeed, an endless amount of interest and 

 utility. The American public now bu3^s over a million dollars' worth 

 of glass vacua a week, but that is the least interesting part of the 

 subject. 



Everybody pretends to know that "Nature abhors a vacuum.*' 

 But he who started that tale merely meant that a good vacuum was 

 hard to produce. As probably no one has ever made a vacuum with 

 less gas molecules in a cubic inch than there are people in the world, 

 we can maintain that perfection in vacua is still precluded by nature. 

 Some studies in vacua will now be reviewed for the purpose of 

 showing that anyone may well do research work not only there but 

 also certainly anywhere else with pleasure and profit. 



We all know that we see at night largely by the aid of vacuum 

 lamps. Through other vacuum lamps, called X-ray tubes, we also 

 see through opaque bodies. The light which illumines our micro- 

 scope specimen has its analogue in the X-ray light, which shows us 

 the crystal structure of matter and the electrical formulas of chem- 

 ical atoms. Our transcontinental wired telephony is possible through 

 vacuum tubes which, in various forms, also permit our radio broad- 

 casting and radio reception from the most remote stations. The 



