Mabch 16, 190(J.] 



SCIENCE. 



431 



spherical representation of their lines of curvature 

 as spherical surfaces.' 



Paul Stackel: ' Die kinematische Erzeugung 

 von Minimal-fliichen (erste Abhandlung) .' 



OsKAB BoLZA : ' A fifth necessary condition for a 



strong extremum of the integral | 'F{x, y, y') dx.' 

 A regular meeting of the San Francisco 

 Section of the society was also held on 

 February 24, at Stanford University. The 

 next meeting of the society will occur on 

 Saturday, April 28. The Chicago Section 

 will hold its nineteenth regular meeting on 

 Saturday, April 14, at the Northwestern Uni- 

 versity Building, Chicago. The date of the 

 next annual meeting of the society has been 

 fixed as Friday and Saturday, December 28-29. 

 The summer meeting and colloquium will be 

 held at Yale University during the week 

 September 3-8. A preliminary announce- 

 ment of the colloquium lectures will be issued 

 in May. W. H. Bussey, 



Assistant Secretary. 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON. 



The 612th meeting was held on January 

 27, 1906. 



Mr. Briggs concluded his communication on 

 ' Centrifugal Methods of Soil Investigation,' 

 pointing out as a third use, to extract the 

 liquid contents of a sample of soil, and fourth, 

 to determine capillary flow of water through 

 soils. 



Mr. W. W. Coblentz, of the Bureau of 

 Standards, then presented by invitation a 

 paper on ' The Infra-red Radiation of Gases.' 

 This part of the spectrum has been investi- 

 gated by photography to 1.2 fi and by phos- 

 phorescent plates to 1.7 /i,; beyond this point 

 the thermopile, bolometer and radiometer 

 have been used up to 15 /*. The speaker had 

 used an unusually sensitive form of the last- 

 named instrument. He exhibited in ten 

 charts the distribution of radiation from 

 various bodies ; as a ' black body,' burning 

 gases, a Welsbach mantle, metals in the car- 

 hon arc and gases in a vacuum tube. 



Previous investigations on emission lines 

 had extended to 2 jn. He had noticed that 

 this was the limit of the lines predicted by our 

 spectral series formulse, hence the object of 



his investigations was to determine whether 

 emission lines could be found beyond this 

 region. 



The main points shown were that inert 

 gases like helium and nitrogen have strong 

 lines just beyond the red, while CO and 

 CO, have a strong emission band at 4.75 ju 

 He showed that for gases in a vacuum 

 tube all lines increase in intensity with 

 increase in current, keeping the pressure 

 constant. On the other hand, for constant 

 current and variable pressure the emission 

 lines at 1 /A have a maximum intensity at 

 about 1.5 mm. pressure, while the intensity of 

 the 4.75 /A band does not pass through a 

 maximum. From this he concludes that the 

 lines at 1 /t belong to those in the visible 

 spectrum, while the 4.75 jct band is not thus 

 related, but seems to be of a thermal instead 

 of an electrical origin. For the arc between 

 metal electrodes and for the salts of the metals 

 in the carbon arc he found no lines beyond 

 % IX. Another interesting point was that the 

 violet vapor of the carbon arc has no infra- 

 red emission lines except possibly at 1 ju. 



Mr. J. F. Hayford then exhibited the new 

 Swiss ' Millionaire ' multiplying machine and 

 discussed the speed and limits of accuracy in 

 practical computing of approximate written 

 multiplication, the slide-rule, logarithms, 

 Crelle's table and machines. The new ma- 

 chine, unlike the familiar Thomas-Burkhardt 

 type, requires both multiplicand and multi- 

 plier to be set up; but then a single turn of 

 the crank is enough for each figure of the 

 multiplier even though the figure be 9. In 

 practise only about half as many manual op- 

 erations are required as on the older machine. 



Each of the papers gave rise to considerable 

 discussion. 



The 613th meeting was held on February 

 10, 1906. 



President Abbe brought forward informally 

 the problem ' How is the peculiar noise asso- 

 ciated with a meteor passing through the 

 upper air produced and communicated to us ? ' 

 No adequate solution has yet b*en given. 



Mr. F. B. Littell described in detail ' The 

 New Transit Circle of Kiel Observatory ' of 



