December 20, 191 7] 



NATURE 



31, 



The Geological Survey of Egypt has just issued the 

 third part of its catalogue of invertebrate fossils in the 

 Cairo Museum, by M. R. Fourtau. It comprises the 

 Cretaceous bivalved shells, and is illustrated by seven 

 beautiful plates. As in the previous parts, M. Fourtau 

 uses specific names in a rather wide sense, being con- 

 vinced that by this means it is easier to appreciate 

 the relationships of a fauna than by multiplying names 

 to denote minute differences. He is also inclined to 

 use familiar and generally adopted names, instead of 

 adhering strictly to the law of priority. His final table, 

 illustrating the' geological and geographical distribu- 

 tion of the fossils, includes 170 forms, of which not 

 more than forty-two are peculiar to- the Egyptian de- 

 posits. Four fresh-water shells are, curiously, found 

 among them. The variable shells of the oysters are 

 -f>ecially interesting, and good drawings of these 

 upv most of the plates. There are parallel varia- 



ns in the different species depending on the several 

 ntical conditions under which they lived. Both the 



;i\ey and the author are to be congratulated on the 

 lass "of new facts they have brought together, and on 

 the admirable manner in which these are published. 



\ OL. xxxiii. of the Coinpte rendu of the Societe de 

 Physique et d'Histoire Naturelle of Geneva contains a 

 paper by Dr. A. Schidlof on a source of error which 

 may be present in the determination of the electronic 

 charge by Millikan's method. When fine drops of 

 mercury are produced by blowing a gas through the 

 liquid, they are found immediately after production to 

 have a density identical with that of the liquid, but 

 after a time tneir apparent density decreases consider- 

 ably owing to the tormation of a layer of oxide or of 

 condensed gas on the surface. Dr. Schidlof points out 

 that the same change may occur in the oil drops used 

 by Millikan, and considers that the numbers given by 

 Millikan show a progressive diminution of the ekc- 

 tronic charge as the experiments continue, which 

 could be explained by the formation on the oil drops 

 of mean radius 510-^ cm. of a layer of thickness 

 10- * cm., of density 0-3. He considers that the true 

 value of the electronic charge lies between 4775 x 10-'" 

 — the value given by Millikan — and 48 x 10-^". 



The Manchester Steam Users' Association has just 

 published its chief engineer's memorandum for 

 1916-17. Among other subjects discussed by Mr. C. E. 

 Stromeyer is the action of caustic liquors on steel plates. 

 Some rings were cut out of a solid plate, and were 

 bored with a tapering hole ; others had a tapering 

 outside, and were forced into the first set of rings 

 so that the external rings were under tension and the 

 internal rings under compression. After treatment in 

 ^ caustic-soda evaporator, the rings were cut up into 

 small segments, and of each ring one short piece was 

 bent inwards and the other outwards. The results 

 were very consistent. All those which were in a com- 

 pressed condition when exposed to the caustic bent 

 double without the least sign of cracking; those under 

 tension, when exposed to the caustic, cracked in in- 

 numerable places when bent. These cracks appeared 

 both on the outer surface, which was in direct contact 

 with the caustic, and on the inner surface, which was 

 not in contact w^th the caustic, but was pressing hard 

 against the compressed inner ring. Evidently, there- 

 fore, the influence of the caustic had penetrated through 

 i in. of metal. Mr, Stromeyer suggests that the 

 action of caustic soda may have been the cause of the 

 cracking of boiler plates in certain instances, and has 

 also several suggestive remarks regarding the design 

 of autoclaves used for the production of certain coal- 

 tar dyes by treatment with strong caustic solutions. 

 A number of autoclaves have been made from drawings 

 found in Continental text-books, and these designs are 

 nearlv all faulty. 



OUR ASTRONOMICAL COLUMN. 

 The Approaching Shower of January Meteors 

 (QuADRANTiDs). — This shower will probably reappear 

 on the nights following January 2 and 3. The best 

 time to observe it will probably be on the early evening 

 j of January 3. Mr. T. W. Backhouse, of Sunderland,. 

 j who has devoted much attention to this meteoric sys- 

 tem during a long period of years, concludes that the 

 maximum will occur on the morning of January 3. 

 I At that time, however, the gibbous moon will be shin- 

 ' ing and high in the sky. On the evening of the date 

 ; mentioned our satellite will not rise until between 

 j 10 and II p.m., and in the dark sky between about 

 j 5.30 and 7 p.m. meteors should be abundant. The 

 radiant point at 232"^ + 52° (8° S. of t Draconis) will 

 be due north at about 8.40 p.m., at an altitude of 

 ! only 14° seen from the latitude of Greenwich. 



The Quadrantid shower is sometimes very rich, 

 though its principal activity is of very brief duration, 

 and it is seldom well observed owing to the generally 

 clouded English skies at this particular period of the 

 year. 



Observations of /3 Lyr.^. — A valuable series of ob- 

 servations of the well-known variable star, P Lyrae, 

 has been made at Catania by A. Bemporad {Me.m. Soc. 

 Spett. Ital., September-October, 1917). The principal 

 mean results of the observations during igii-12 are 

 as follows :— 



Interval 

 Mag. Julian day in days 



First principal minimum ... 4*39 2419,22751 ^^_ ^ 

 First maximum 3-54 220- S7 SjZl'^^l 



Second minimum ... ... 387 



Second maximum ... ... 3 "54 



Second principal minimum... 4'39 



'^-3075 

 -^3 700 



233-65 



240-43 ^^i"«" 



The total range of variation was thus 085 mag,, and 

 there were indications that the second maximum was 

 brighter than the first by about 002 mag. While the 

 light-curve about the principal minimum was practic- 

 ally symmetrical, the descent to the secondary mini- 

 mum was more rapid than the rise to the succeeding 

 maximum. 



Radial Velocities of Star Clusters. — At the 

 Albany meeting of the American Astronomical Society 

 Dr. Slipher announced some important results which 

 he has obtained relating to the radial velocities of star 

 clusters (Journ. R.A.S., Canada, vol. xi., p. 335). 

 The instrumental equipment was that previously em- 

 ployed by him, with marked success, for spiral nebulae. 

 Ten clusters have been observed, and the velocities 

 range from —410 to +225 km. per sec. The 

 mean velocity, taken without regard to sign, is 

 150 km. per sec. As in the case of spiral 

 nebulae, the high velocities observed suggest the possi- 

 bility that the clusters are distinct from our own 

 sidereal universe. 



Parallax of the Ring Nebula in Lyra. — An attempt 

 to determine the parallax of the central star of the 

 Lyra nebula has been made by Mr. A. van Maanen, 

 with the aid of photographs taken with the 60-in. 

 reflector at Mt. Wilson {Popular Astronomy, vol. xxv., 

 p. 630). Nine comparison stars were utilised, and the 

 resulting relative parallax is given as +0002" ±0005". 

 The absolute parallax would be 0-004', and as there' is 

 practically no doubt as to the association of the star and 

 nebula, this indicates enormous dimensions for the 

 nebula itself, namely, 330 and 250 times the diameter 

 of the orbit of Neptune for the major and minor axes. 

 Taking 14-1 as the visual magnitude of the central star, 

 the above parallax leads to the low value of -f 7-1 for 

 the absolute magnitude. 



NO. 2512, VOL. 100] 



