Apkil 20, 1917] 



SCIENCE 



385 



sure increases from the diastolic to close to the 

 systolic level. And it was shown that under 

 approximately this set of conditions such is 

 actually the case (see Figs. 10 and 11). 



But even if Boyle's law did (and it actually 

 does not) determine a diminution instead of 

 an increase in the amplitude of oscillations 

 with increasing compressing pressure, the de- 

 velopment of the theory of compression oscil- 

 lations would not have been afPected in the 

 least. For in the further development of the 

 theory it is shown (Figs. 12 and 13) that under 

 the influence of additional conditions obtain- 

 ing in sphygmomanometry the consequences 

 of Boyle's law become relatively so insignif- 

 icant that the amplitude of oscillations, in- 

 stead of increasing, as the compressing pres- 

 sure rises from the diastolic to the systolic 

 level, actually decreases. 



Joseph Erlanger 



Washington ITniversitt Medical School, 

 St. Louis, Mo. 



the unit of pressure 

 To THE Editor op Science: The announce- 

 ment that the French Meteorological Service 

 has, beginning January 1, 1917, decided to 

 publish atmospheric pressure data in units of 

 force instead of millimeters as heretofore, 

 makes it necessary once more to call attention 

 to the fact that the proper unit for the expres- 

 sion of pressure is not the millibar but the 

 hilohar. The scientific reasons for this have 

 been given elsewhere at length. Another valid 

 reason, however, may be now mentioned. 



There has recently been developed a new 

 type of condensation high-vacuum pump. I 

 refer to that of Professor Langmuir. Pres- 

 sures as low as 10"^ bar have been obtained; 

 and there is little doubt that very much lower 

 pressures can be produced by cooling the bulb 

 to be exhausted, in liquid air, so as to decrease 

 the rate at which gases escape from the walls. 

 The unit har is here used (and I believe this 

 is the practise of the General Electric Com- 

 pany and will of course be followed by physi- 

 cists, chemists and others working on allied 

 problems) in its right sense, namely, the ac- 

 celerating force of one dyne per square centi- 

 meter. This is 10"'' megabar. In the case of 



this type of pump we have a pressure of 10"^'- 

 megabar or 10"'-^ standard atmosphere. 



The millibar then in daily use becomes what 

 it properly is, 10"^ bar. The European Weather 

 Services trying to express atmospheric pres- 

 sures in millibars are in error, and the correct 

 values are one million times greater. 



Fortunately, it is an easy matter to change 

 mh to Teh. And this should be done on all 

 tables, charts, etc., published by European 

 meteorologists. Alexander McAdie 



A RELIEF MAP OF THE UNITED STATES 



To THE Editor of Science : With reference 

 to the suggestion in Science of March 9, rela- 

 tive to a large relief map of the United States, 

 may I be allowed to state that this is a matter 

 which I often discussed with the late E. E. 

 Howell, who at one time had it under serious 

 consideration? It was then my view, to 

 which I still adhere, that there was a limit 

 in size for such objects, beyond which nothing 

 was gained. This was particularly impressed 

 upon me some years ago while studying some 

 of the maps of celebrated battlefields in Ger- 

 man museums. In these large models, details 

 toward the center, on account of distance from 

 the eye, were as inconspicuous as though on 

 a smaller scale and closer at hand. In short, 

 the efl^ect of the enlarged map was wholly lost 

 owing to the necessary distance of the ob- 

 server. A small map near at hand would be 

 much less expensive, and fully as satisfactory. 



With Dr. Clarke's remarks in Science for 

 March 23 I fully agree, data not being at 

 hand for anything but the most general topo- 

 graphic features over a large portion of the 

 area of the United States. The plan, as it 

 appears to me, is wholly impracticable. 



George P. Merrill 



TJ. S. National Museum, 

 Washington, D. C. 



QUOTATIONS 



RESEARCH IN MEDICAL SCHOOLS 



An important report^ in this issue of The 

 Journal shows that of the twenty-six founda- 



1 * ' Medical Research in Its Eelation to Medical 

 Schools." A Eeport by Drs. Frederic S. Lee, 

 Eiehard M. Pearce and W. B. Cannon, composing 



