592 



SCIENCE. 



LN. S. Vol. V. No. 119. 



creased pressure, corresponding to a rise in the 

 boiling point of carbon. The radiation from 

 the crater was measured with a radiomicrom- 

 eter. Since the radiation varies as the fourth 

 power of the temperature, a slight change in 

 the latter should be noticeable. The experi- 

 ments were not definitive, on account of the 

 many difficulties encountered, but seemed to 

 show that the temperature remained constant 

 throughout a range of pressure of from one to 

 seven atmospheres. At any rate, the constancy 

 was sufficient to practically disprove the boiling- 

 point idea. Among the chief difiiculties to be 

 met were connection currents in the apparatus, 

 which rendered the gases so opaque as to sug- 

 gest to the writers a new explanation of sun 

 spots. The paper has the additional interest of 

 indicating that temperature eflfects can not play 

 an important part in the shifting of lines in 

 metallic spectra when pressure is applied to the 

 arc. 



Preliminary Table of Solar Spectrum Wave- 

 lengths, XVII.: By Heney A. Rowland. 



On the Comparative Value of Refracting and 

 Reflecting Telescopes for Astrophysical Investiga- 

 tions : By George E. Hale. The paper, as is 

 indicated by the title, is a discussion of the rela- 

 tive merits of the two forms of instruments men- 

 tioned. In addition to economy, freedom from 

 chromatic abberation, and other advantages 

 sometimes urged in favor of reflectors. Professor 

 Hale brings forward that of their relative free- 

 dom from absorption. The effect of this in 

 large refractors is discussed in the above paper 

 by Dr. Vogel, and is shown to increase with 

 the size. Since the percentage of absorption of a 

 reflector is independent of its dimensions, this 

 factor is of great importance where large aper- 

 tures are concerned. The paper is accompanied 

 by an interesting diagram, which shows, among 

 other things, that for linear apertures greater 

 than 90 cm. the photographic [light-gathering 

 power of a reflector exceeds that of a refractor. 



On a New Form of Mounting for Reflecting 

 Telescopes Devised by the Late Arthur Coivper 

 Ranyard: By F. L. O. Wadswoeth. The 

 writer discusses some developments of the idea 

 of the Cassegraiman Cond6 proposed by Mr. 

 Ranyard. Several forms of mounting are con- 

 sidered. In every case, with one exception. 



the polar axis is of the fork type. A mirror at 

 the intersection of the polar and declination 

 axis is so arranged that its plane always bisects 

 the angle between the telescope and polar axis, 

 so that light from the small convex mirror is 

 always thrown up or down the polar axis 

 (which is hollow), as may be desired. 



A Support System for Large Specula : By G. 

 W. RiTCHEY. In this article Mr. Ritchey de- 

 scribes a support system designed to reduce to 

 a minimum the effects of flexure in large mir- 

 rors. The system is in reality a double one: 

 1. The back support. 2. The edge support. 

 In the first system the mirror is considered as 

 divided, by cylindrical surfaces perpendicular 

 to the back of the mirror, into twelve parts of 

 equal mass. Each part rests upon a support. 

 Nine of these supports are counterbalanced in 

 all positions by weighted levers, while the re- 

 maining three rest upon the cell. It is evident 

 that if all twelve supports were counterbalanced 

 the mirror would be in equilibrium in any posi- 

 tion close to its normal one. If three of the 

 supports are fixed, however, the nine remain- 

 ing counterweights will be unable to take any 

 of the weight ofFof the fixed supports which will, 

 therefore, determine the plane of the mirror. 

 The mirror will, therefore, float in a fixed plane. 

 The edge support is designed upon the same 

 general principles. There is reason to believe 

 that the plan will combine with a perfect flota- 

 tion support, a degree of stability heretofore 

 unattained in speculum mounting. 



Oxygen in the Sun : By Lewis E. Jewell. 

 See foot-note to abstract of App. J, December, 

 1896, in Science, March 19th. 



Minor Contributions and Notes, Reviews, Bibli- 

 ography. 



SOCIETIES AND ACADEMIES. 



zoological club, university of CHICAGO, 



MEETING FEBRUARY 10. 



ABSTRACTS OF PAPERS PRESENTED. 



On the Morphology of the Skull of the Pelycosauria 

 and the Origin of the Mammals.* By G. Baur 

 and E. C. Case. 



*A fuller account of this paper has just been pub- 

 lished in Anatom. Anzeiger, XIII. Band., No. 2 and 5, 

 January 30, 1897, pp. 109-120, with three figures of 

 the skull. 



