544 



SCIENCE 



[Vol. LV, No. 1429 



undertakes to eliminate these sources of error by 

 the measurement of the cells: 



(1) Au, AuCl, KCl, (XM), AgCl, Ag. 



(2) Au, AuCl, HCl (XM), H, (1 atom.) 



The direct value obtained for the second cell will 

 be checked by an indirect method which em- 

 ploys Cell (1). Cells employing Au^O in KOH 

 solution are also being measured. 



A study of some unusual habits of loulfenite: 

 F. S. Waktman. This paper briefly discussed an 

 extremely flat third order pyramid found to be 

 somewhat common on wulfenite crystals in the 

 Southwest. It is characteristic, although its sym- 

 bol varies' from 1-7-75 -to 1-7-98. Another unusual 

 crystal having the prism faces well developed was 

 also described. 



A studxj of the catalytic effect of metallic cop- 

 per upon the evolution of hydrogen from acids 

 hy base metals: Doeotht G. Andrews. 

 Geology 



Sketch of the geology of the Dos Calezas 

 Mountains of southwestern Arizona: C. J. Sakle. 

 The range is described as a homoclinal fault-block 

 structure, dipping southwestward, with northwest- 

 southeast trend, about 25 miles long, Avith greatest 

 width midway of nearly 10 miles and maximum 

 height of approximately 8,300 feet in the cen- 

 tl-ally situated twin peaks from which it takes its 

 name. Besiduary piedmont gravel slopes incline 

 away from the range to the broad waste-filled 

 Sulphur Springs valley on the southwest, and to 

 the similar San Simon valley on the northeast. 

 The Dos Cabezas range forms a common erogenic 

 structure mth the larger Chiricahuas to the south. 

 The relations and character of the formations and 

 structures reveal a history extending back, pos- 

 sibly to Archean time, and seem to show four 

 periods of mountain making; two pre-Cambrian, 

 and distinctly batholithic; one at the close of the 

 Paleozoic, of marked warping, and possibly with 

 faulting; and a fourth of marked volcanicity and 

 profound faulting, with some batholithic intru- 

 sion.. The last produced the present Dos Cabezas 

 range. The first three were followed by planation 

 and subsequent sedimentation. Tertiary erosion 

 developed a rock pediment and piedmont gravel 

 slopes, mature dissection extending to the heart 

 of the range. In turn Pleistocene erosion deeply 

 sculptured the piedmont area. The sedimentaries 

 include a heavy, pre-Cambrian quartzite, Cam- 

 brian including an upper limestone member, 

 Ordovieian (Beekmantonian), Mississippian, 

 Pennsylvanian, Comanchean (with marine leaf). 

 Tertiary piedmont gravels and recent alluvials 



(fan and stream flat deposits). (Preliminary and 

 with permission of the director of the Arizona 

 Bureau of Mines). 



Astronomy 



The application of spectrum analysis to studies 

 of the planets: V. M. Slipher. A discussion of 

 the use of the spectroscope in studying rotation 

 and motion of the plants and the constitution of 

 their atmospheres. Evidence of water vapor in 

 the atmosphere of Mars was presented. 



Martian polar rifts: G. H. Hamilton. A dis- 

 cussion of rifts in the polar cap of Mars, ob- 

 served during the successive oppositions of 1916, 

 1918 and 1920; and accompanied by lantern 

 slides of drawings illustrating rifts. The belief 

 was expressed that these rifts confirm Lowell's 

 contention that there is vegetation on Mars, since 

 it is assumed that they are caused by the heat 

 given off from growing vegetation. This con- 

 clusion is drawn from the apparent similar con- 

 dition produced on the earth by vegetation grow- 

 ing under the snow. 



Methods used at the Lowell Observatory in 

 studying Mars and other planets: E. C. Slipher. 

 The technique of astronomical photography was 

 explained. The necessity for enlarging the image, 

 correcting for ehromatism with the yellow 

 filter, and using specially sensitized plates was 

 pointed out. The speaker also discussed the time 

 exposure necessary, which varies from one third of 

 a second to 25 or 30 seconds. In closing, it was 

 declared that if due allowance be made for the 

 limitations of the two methods, each is useful as 

 a check on the other. 



Progress in photographic observations of nebulce 

 with the 40 inch Lowell reflector: C. O. Lamp- 

 land. The modern telescope has increased greatly 

 the number of stars and nebulae, and dark nebulae 

 have also been identified. Among astronomers 

 considerable difference of opinion exists as to the 

 depth of OUT stellar galaxy, some placing its 

 greatest diameter at 300,000 light years; others 

 at about one fifth of that. It w-as pointed out 

 that spiral nebulae may be stellar systems — island 

 universes — outside our own galaxy. Various argu- 

 ments for and against the "Island Universe" 

 theory were offered, among the former being the 

 discovery by V. M. Slipher in 1912 of high space 

 velocity and axial rotation. Yet, despite these 

 high space velocities, their proper motion is very 

 small. Also, their spectrum differs from the 

 spectra of the stars in our system, it resembling 

 the coalesced light of many stars at such great 

 distances that the light of one star can not be dis- 



