474 



SCIEJSrCE. 



[Vol. VI., No. 147. 



transit. In the latter case Professor Holden points 

 out the necessity {Astr. nachr., 2690) of changing 

 the iUumination of the field, with the change of 

 screen, so that each magnitude may show against 

 its customary degree of color, or brilliancy of back- 

 ground. Such screens may also be used for photo- 

 metric purposes when once their co-efficients of 

 transmission have been determined. Those having 

 occasion to use them in this way will do well to 

 consult a paper by Professor Langley (Amer. 

 journ. sc, xxx. 210) on this subject. In this it is 

 shown that the effective transmission co-efficients 

 are decidedly different according as the luminous 

 image is an extended surface, or practically a point 

 like a star. In the latter case there is a central 

 image surrounded by a system of diffraction 

 images, into which a large part of the light goes ; 

 so much so, that Professor Langley found that a 

 screen (of which one and two thicknesses trans- 

 mitted .47 and .21 respectively of the full light 

 upon a surface) gave only .18 and .02 for one and 

 two thicknesses respectively, when measured by 

 the brilliancy of the central image of a small pin- 

 hole as a source of light. 



Comparison stars. — M. Folic, director of the 

 observatory of Bruxelles, Belgium, announces that 

 he also is ready (see Science, vi. 427) to determine 

 the apparent places of comparison stars for comets 

 and asteroids, if those desiring such determina- 

 tions will communicate the approximate star- 

 places to him. 



Rhodope rediscovered. — On Oct. 3 Pahsa found 

 and observed (16G) Rhodope, the search for which 

 we before noted {Science, vi. 333) as the occasion 

 of the discovery of (250). 



The coast-survey system of longitudes. — In 

 Appendix 11 to the coast-survey report for 1884, 

 Assistant Schott rediscusses all the telegraphic 

 longitude work thus far done by the survey, includ- 

 ing tlie tlrree transatlantic cable-determmations of 

 1866, 1870, and 1872. The whole work now ui- 

 cludes 158 individual determinations of A/. Of 

 these, 53 belong to a network covering 33 stations 

 extending from Paris to Omaha, thus furnishing 

 21 rigorous conditions to be fulfilled by the longi- 

 tudes of the 33 stations, a much stronger system 

 than that discussed in the report for 1880. The 

 average probable-error of single determination of Al, 

 including every thing since the origin in 1846, comes 

 out 0^.038, as determined a priori from the ob- 

 servations themselves, or only 0^.016 as the average 

 since 1878, when improved methods were intro- 

 duced. From the residual corrections, however, 

 which result from the discussion, as necessary to 

 make the 53 values of A a satisfy the 21 rigorous 

 conditions, the probable-error of a single AZ comes 

 out 0^.048, indicating, as compared with 0^.038, 



that there are still some outstanding errors, prob- 

 ably of observers' personal-equation, which the a 

 priori probable-errors do not cover. There is 

 only one resulting correction to an observed value 

 which reaches 0^.1, while in the latest adjusted 

 system of European longitudes, which involves 59 

 measures with 26 conditions, although the average 

 probable-error of a AA comes out only 0^.035, yet 

 there are six corrections to observed values whicli 

 exceed 0^.1. It will be seen that the American 

 work compares very favorably with the European, 

 while it includes the three difficult transatlantic- 

 cable links. Mr. Schott has accepted the decision 

 of the Meridian conference, and in his final table 

 prints longitudes east of Greenwich as -1-, and 

 west as — . He has also gone through the tedious 

 process of computing the probable-error of a func- 

 tion of adjusted values for the longitudes of Cam- 

 bridge and Washington, which come out — 

 Cambridge, a = — 4l^ U"' 30^.993 ± 0^.041, 

 Washmgton, A = — 5^ 8"^ 12^.038 ± 0^.042. 

 An interesting paragraph at the end shows that 

 the rather remarkable agreement in the three 

 transatlantic determinations of the longitude of 

 the Harvard college observatory, as given in the 

 report for 1874, was more an agreement of adjust- 

 ment than of observation, and that the observed 

 values have really a range of 0M3. This is the 

 most complete discussion of a network of longi- 

 tude determinations yet made, and it well sustains 

 the liigh reputation which the scientific work of 

 the coast survey bears at home and abroad, very 

 much of which is due to the thorough work of 

 Assistant Schott and his efficient computing di- 



NOTES AND NEWS. 



What is in some points a remarkable circular 

 is prefixed to the current number of the Zeitschrift 

 filr philosophie itnd philosophische kritik, the 

 most conservative and old-fashioned of periodicals. 

 The management of the zeitschrift announces a 

 new policy in view of the tendency of the best 

 thought of the day, which is "to strive for a re- 

 vival of the idealistic view of the universe, it being 

 compelled thereto not less by practical than by 

 scientific considerations." Therefore the polemi- 

 cal character of the zeitschrift wiU cease, the 

 reason for it having been removed. In the second 

 place, the vast amount of criticism will give way 

 to explanatory sketches and sympathetic notices of 

 new books and results, so that no investigation 

 may have injustice done it at the hands of a re- 

 viewer of an opposite school. More attention is ta 

 be paid to the historical aspect of philosophy and 

 the soc-ial sciences, and in especial wiU the work 

 of countries other than Germany receive its share 



