832 



SCIENCE. 



[N. S. Vol. IV. No. 101. 



Against the elementary nature of argon and 

 helium stands the difficulty of placing them 

 in the periodic system. He does not agree 

 that the argument drawn from the ratios of 

 the specific heats is conclusive as to the 

 molecule of argon or helium containing 

 only a single atom. The density of argon, 

 19.94, being less than that of N3, 21.06, he 

 accounts for by the possibility of the pres- 

 ence of helium or some other inert gas. Of 

 positive arguments in favor of his theory he 

 gives none, but suggests that a determina- 

 tion of the atomic heat would decide the 

 question. He inclines to the view that the 

 constituents of helium were formed from 

 hydrogen in accordance with Front's law. 

 The latest contribution to a systematic 

 arrangement of the elements is an article 

 by Kichard Lorenz in the Zeit. Anorgan- 

 ische Chemie, on 'Twin Elements.' The 

 author gives this name to elements which 

 have nearly the same atomic weight, re- 

 semble each other in occurrence and chemi- 

 cal behavior, and are with difficulty sepa- 

 rated from each other. Such twins are 

 sodium-magnesium, cobalt-nickel, phos- 

 phorus-sulfur. The atomic weights of each 

 twin differ from those of the next twin by 

 four units. In some instances a single 

 member only of the pair exists or is known, 

 as chlorin is the only element of the twin 

 which lies between phosphorus-sulfur and 

 potassium-calcium. Lorenz develops from 

 this a germinal rule. Taking as his start- 

 ing point the atomic weights three and four, 

 the latter corresponding to helium, he pro- 

 ceeds by successive increments of four. Of 

 the second pair (7, 8), lithium only is 

 known ; the third twin is (11, 12) boron- car- 

 bon ; of the fourth only oxygen is known ; of 

 the fifth (19, 20), we have fluorin, and per- 

 haps argon. Up to the atomic weight of 

 128, thirty-nine elements correspond to this 

 germinal rule, while there are ten elements 

 whose weights do not fall within the limits 

 of any pair. Fourteen of the thirty-two 



twins have but one member, four twins 

 have no known member, and one twin, 

 cobalt-nickel, is displaced one unit from its 

 theoretical value. Of the elements of higher 

 atomic weight, ten of the best known follow 

 the rule, while four do not. The author 

 seems to indicate his opinion that this ger- 

 minal rule expresses the composite nature 

 of the elements, and suggests that the ele- 

 ments which conform to it may be built up 

 analogous to one series of hydrocarbons, 

 while the exceptions may be built up on a 

 different plan. 



The article recalls two anonymous con- 

 tributions to the American Supplement to 

 the Chemical News for 1869 (pp. 217 and 

 339) on the ' ]S"umerical Relations of the 

 Atoms ' and the ' Pairing of the Elements,' 

 where very similar ideas were suggested. 

 J. L. H. 



ASTRONOMICAL NOTES. 

 In our issue of November 15th we called 

 attention to an article by Dr. Marcuse, of 

 Berlin, giving an account of a series of ob- 

 servations made by him with the new 

 photographic zenith telescope belonging to 

 the Geodetic Commission. We have now 

 received Frof. Albrecht's report upon the 

 performance of the same instrument, which 

 has been mounted at Fotsdam side by side 

 with the old visual instrument. This ar- 

 rangement has enabled Herr Schnauder 

 and Dr. Hecker to carry out a simultaneous 

 series of observations with the two instru- 

 ments, and using the same stars. The re- 

 sult of the research was not favorable to the 

 photographic instrument, since it necessi- 

 tated much extra labor, without any suffi- 

 cient compensating advantage in the ac- 

 curacy attained. It will be remembered 

 that the Geodetic Commission proposes to 

 establish four permanent observing stations 

 on the same parallel of latitude, but differ- 

 ing nearly 90° in longitude, in order to get 

 a continuous and very accurate determina- 



