314 



SCIENCE 



[N. S. A'OL. XLVII. No. 1213 



portioned thermal resistance between the heat- 

 receiving surface and the boiling liquid. This 

 ■was shown by the writer in an article on " A 

 New Principle in the Flow of Heat" in the 

 Journal of the Franldin Institute, January, 

 1918, page 75, and another in Power for Jan- 

 uary 1, 1918. In this way the writer has 

 transmitted heat from a flame to water from 

 25 to 30 times as fast through the same area 

 of surface. 



It seems likely that this supposed high-re- 

 sistance film is not a true thermal resistance, 

 its estimated resistivity being many times that 

 of good insulators liie felt, but that the true 

 explanation is that when hot gases impinge 

 on a relatively very cold surface much of the 

 heat is reflected and but little is transmitted. 

 Perhaps the transference of the momenta of 

 the moving molecules constituting heat is the 

 explanation, in which case that part of the 

 energy which is not transmitted is reflected. 



Carl Hering 

 Philadelphia, Pa., 

 February 15, 1918 



THE AURORA OF MARCH 7, 1918 



Those who saw the aiirora of August 26, 

 1916, did not expect to see such a display re- 

 peated within a life time, but on March 7, 

 1918, there was a similar spectacle which from 

 reports must have been visible over practically 

 all of the northern hemisphere of the earth. I 

 first noticed the aurora low down in the north, 

 about 7 P.M., but in half an hour clouds had 

 come, which continued for an hour or so. At 

 9.30 I happened to be out of doors and saw 

 that something star'tling was in prospect, as the 

 sky was clear and the aurora was growing 

 rapidly. The general effect and appearance of 

 the display was accurately described by Dr. 

 Tomlinson of our geology department,^ and I 

 shall limit my account to the determination 

 of the position of the radiant or apparent 

 focus of the auroral streamers. It was very 

 striking that just when the display was at its 

 maximum the streamers seemed to come from 

 Saturn. 



In the following notes Central Standard 



1 Science, March 22. 



Time, 6 hours slow of Greenwich is used, the 

 position being latitude 40° 6' north, longitude 

 88° 13' west. 



9h. 31m. Streamers rising. Cloud-like form in 

 southeast. 



9h. 36m. Eadiant exactly at Saturn. Half of 

 sky or more covered. To west and over Jupiter a 

 broad band of red, 10° or 15° wide. This is south- 

 ern edge of the aurora in that direction. 



9h. 41m. Eadiant 2° north of Saturn. 



9h. 44m. Radiant 2° northeast of Saturn. 



9h. 46m. Badiant fainter. 



9h. 51m. Eadiant has about disappeared. 



9h. 51m. All of light is now below Polaris. 



lOh. 38m. Only faint glow low down. 



'So further display was noted by our observ- 

 ers at the telescope, who worked until several 

 hours after midnight. 



Averaging the three estimates, we have that 

 at 9h. 40.3m. the radiant was l°.l north and 

 0°.5 east of Saturn. The magnetic elements 

 for Urbana are : declination 3° 13' east, dip 

 71° 5', determined by Mr. Merrymon in 1917, 

 and kindly communicated by the superintend- 

 ent of the U. S. Coast and Geodetic Survey. 

 From the ephemeris position of Saturn, we 

 readily find then for comparison: 



Hour 

 Declination Angle 



Magnetic zenith -{- 21°.2 -f- l°.l 



Radiant -1- 20°.l -1- 0°.2 



Difference l°.l 0°^ 



The result shows that within the error of 



estimate the apparent radiant or focus of the 



auroral streamers was at the magnetic zenith, 



which agrees with what was observed in 1916. 



Joel Stebbins 



TJniversitt op Illinois Observatoet 



From reports it is learned that the aurora 

 borealis seen here on the evening of March 7 

 was observed at the same hours from New York 

 City to Salem, Oregon, also at St. Louis and 

 as far south as Lat. 36° N., in North Carolina. 

 It was probably seen by observers over an area 

 of greater extent in the United States and oc- 

 curred also in Europe. This synchronous oc- 

 currence seems to indicate a widespread uni- 

 formity of the atmospheric conditions which 

 produced it and to offer additional evidence 



