164 



SCIENCE. 



[N. S. Vol. III. No. 57. 



The old question as to the existence of 

 Volta's ' contact electricity ' is again taken up 

 by C. Christiansen {Wied. Ann., 56, 1895.) who, 

 with an apparatus employing the drop electrode, 

 has investigated the behavior of magnesium, 

 aluminum, cadmium, zinc, tin, lead, iron, 

 platinum, nickel, copper, mercury and carbon 

 in atmospheric air, hydrogen, carbonic acid gas 

 and oxygen, and arrives at the conclusion that 

 oxygen may be, if it is not always, the cause of 

 potential differences between metals in contact, 

 and he is of the opinion that it is a polarization 

 by the gas, just as oxygen or hydrogen polarizes 

 platinum. 



G. Meyer investigated an allied subject with 

 the Lipmann capillary electrometer testing the 

 combinations of mercury, and lead, copper, tin 

 and zinc amalgams in sulphuric and hydro- 

 chloric acids, potassium chloride, iodide and 

 sulphocyanide, and sodium sulphide. A fur- 

 ther contribution to our knowledge of the 

 dielectric constant is made by S. Silberstein, 

 who has determined this constant for various 

 mixtures of benzol and phenylethylacetate, and 

 finds that the results agree well with the conclu- 

 sions derived from theoretical considerations. 

 {Wied. Ann. Vol. 56, 1895.) 



W. H. 



ASTRONOMY. 



The Astronomical Society of the Pacific has 

 just published an account by Prof. Tucker, of 

 the methods he is using for the investigation of 

 the division errors of the Repsold circle of the 

 Lick Observatory. We are glad to see the 

 principle of using the auxiliary circle for the 

 purpose of investigating the principal circle. 

 This plan has many advantages, but its weak 

 point of course is that the two circles are at some 

 distance from each other and are read by difl'erent 

 microscopes. It may not be generally known 

 that a transit circle was constructed by Messrs. 

 Cooke & Sons for Mr. Newall, under the super- 

 intendence of Mr. Marth, in which the divisions 

 of the two circles could be brought into the 

 field of view of one microscope simultaneously. 

 The errors of that circle, however, were never 

 investigated. 



But it may be questioned whether the re- 

 sults ever justify the expenditure of the great 

 amount of time and labor involved in such in- 



vestigations as that of Prof. Tucker. Probably 

 the same amount of energy given to observa- 

 tion of the stars, taking care of course to shift 

 the circle from time to time, would be of greater 

 benefit to astronomical science. Even if the 

 division error of any given line could be deter- 

 mined with complete precision with the tele- 

 scope pointed at the zenith, this division error 

 would not hold true when the telescope is 

 directed elsewhere. Nor is this brought about 

 by flexure alone. It is found that if we deter- 

 mine the division errors of a straight scale, 

 these errors are completely changed when the 

 scale is reversed end for end. No doubt una- 

 voidable diflerences in the illumination and the 

 eye of the observer are responsible for these 

 unfortunate facts. But facts they are, and the 

 cause of much wasted labor. 



The 1890 volume of the Annuaire published 

 by the Bureau des Longitudes has been issued. 

 It contains the usual mass of material devoted 

 to astronomical and other science. Among the 

 appendices are articles by MM. Cornu and Jans- 

 sen, which are of general interest. The list of 

 members of the Bureau contains the names of 

 two Americans : Dr. B. A. Gould and Mr. G. 

 Davidson. The latter gentleman is described as 

 'directeur de I'observatoire de Californie et du 

 Service geodesique.' H. J. 



GENEKAL. 



The herbarium of the late Prof Daniel Cady 

 Eaton has been presented by his family to 

 Yale University. The herbarium contains over 

 65,000 sheets, and is especially rich in North 

 American ferns and mosses. 



The library of the University of Pennsyl- 

 vania has acquired the scientific library of 

 the late Prof. John A. Ryder. It has also 

 secured the Bechstein Library of German Phil- 

 ology and Literature, containing about 20,000 

 bound volumes and pamphlets. 



Nature states that Prof. Sollas, F. R. S., will 

 leave in March for Sydney, to take charge of an 

 expedition that is being dispatched to make deep 

 borings in a coral atoll. The scheme, which is 

 supported by a strong scientific committee, has 

 been financed by the Royal Society to the ex- 

 tent of £800 ; and the government are placing 

 a gunboat at the disposal of the party, to convey 



