June 27, 1902.] 



SCIENCE. 



1013 



the tangents as the basis of a sheaf of rays 

 of the second order, the original five points 

 are shown to be points of contact. Revert- 

 ing to the original five points, construc- 

 tion for a sixth point is made, and the tan- 

 gent at that sixth point is obtained; this 

 tangent is shown to belong to the sheaf of 

 rays of the second order furnished by the 

 five original tangents. It was also shown 

 that the curve is uniquely determined 

 whatever two points be selected as radiant 

 points; and an analogous proposition was 

 established with regard to the sheaf of 

 rays. 



On the Matrix Analysis of Quantics and 



Their Concomitants: Dr. J. C. Glashan. 



A development of the consequences of 



applying to the operand as well as to the 



operator the notation of matrices. 



Forms for the Abelian Integrals of the 

 Three Kinds: Dr. J. C. Fields. 



A Theorem Regarding Determ/inants with 

 Polynomial Elements: Professor W. H. 

 Metzler. 



Generalization of a theorem of Muir's 

 (Messenger of Math., No. 153, 1884) omit- 

 ting the restriction that the number of 

 terms in each element of the determinant 

 must be greater than the number of con- 

 stituents in a row. 



PHYSICS. 



On the Use of the Wheatstone Stereoscope 

 in Photographic Surveying: Capt. B. 

 ■ Deville. 



Description of an instrument proposed 

 for drawing a topographical plan by me- 

 chanical means from a pair of stereoscopic 

 photographs. 



The Neutral Axis of Beams Under Trans- 

 verse Loads: Professor H. T. Bovet. 

 Experiments with a new Extensometer. 

 The assumptions of the text-books are veri- 

 fied for a cast-steel beam of square cross 

 section, but not for a T-beam. 



Soli-Lunar Time: Mr. G. W. McCreadt. 



The average date of the first full moon 

 in every decade for 4,000 years. 



The Potential Difference Required to Pro- 

 duce Discharge in Air and Other Gases: 

 Mr. W. R. Care. 



Experiments carried out under the di- 

 rection of Dr. J. C. McLennan, with air, 

 hydrogen, carbon dioxide, acetylene, hy- 

 drogen sulphide, nitrous oxide, sulphur 

 dioxide and oxygen. The law governing 

 electric discharges between parallel plates, 

 in a uniform field, in any gas, for pres- 

 sures at and below the critical pressures, is 

 that which Paschen found to hold with 

 spherical electrodes for high pressures, 

 viz., that with a given spark potential, the 

 pressures at wliich discharge occurs is in- 

 versely proportional to the distance be- 

 tween the electrodes. 



The values of the spark potentials are 

 not influenced by the material or size of 

 the electrodes; and the minimum spark 

 potential is independent of the pressure 

 and of the distance between the electrodes, 

 always provided that the discharge is com- 

 pelled to pass in a uniform field. 



Penetrating Rays from Radium: Pro- 

 fessor E. Rutherford. 

 Experiments showing the passage of the 

 rays through from eight to ten inches of 

 iron. The ionization produced by the rays 

 after emerging from the iron shows that 

 they must be regarded as consisting of 

 negatively charged particles. Photo- 

 graphic methods are being applied to de- 

 termine the magnetic defieetion of the 

 rays. 



Radio-active Emanations from Thorium 

 and Radium: Professor E. Ruther- 

 ford. 



Resume of a nmnber of recent experi- 

 ments by the author. 



