174 SCIENTIFIC RECORD FOR 1884. 



tudes ; and, besides, it fuinisLes the first available data for a rigorous 

 comparison and reduction of all i)revious catalogues to a common truly 

 photometric scale. Many interesting results of these comparisons are 

 promised in part ii, some of which were outlined by Professor Picker- 

 ing at the September meeting of the American Association. The bulk 

 of the volume is taken up Mith chapter v, which contains the general 

 catalogue and its accompanying explanations. This has been more re- 

 cently issued separately, under ihe name of the Harvard Protometry, 

 and it should be in the hands of every professional and amateur astron- 

 omer at once the world over. In it is condensed in remarkably con- 

 venient form a vast mass of detailed information. Beside the results 

 of the Harvard photometric work with the number of observations and 

 the resulting probable error of the mean, aic given the results of a 

 series of eye estimates undertaken speciallj' to com[)are the two methods. 

 In columns alongside are the corresponding magnitudes in the four 

 l^rincipal standard catalogues of magnitudes, the Uranometria Nova of 

 Argelander, the Atlas Coelestis of Heis, the Ihirchmitsterung of Arge- 

 lander, and the Uranometria Argentina of Gould. On the right-hand 

 l)age are the dift'erences of magnitude between the Harvard Protometry 

 and fourteen other catalogues of eye estimates, and the three photo- 

 metric catalogues of Seidel, Wolff", and 0; S. Peirce, for the compara- 

 tively small number of stars contained in these last ; also a column de- 

 voted to the colors of the stars so estimated by Mr. W. S. Franks, of 

 the English Eoyal Astronomical Society, in a special series of observa- 

 tions for that purpose. Columns of reference numbers to the original 

 series for each observation, and also the residuiil of each from the mean, 

 are given in every case, so that the whole results lie open at a glance 

 all in one place. In printing these residuals, a novel use of type is 

 made, the negative ones being in italics, thus saving the sjiace of plus 

 and minus signs and giving a much better ap])earance. Where the 

 residual is greater than nine and less than twenty, only the right-hand 

 figure is printed, but in heavy-faced type. The volume is from the 

 Cambridge University Press of John Wilson & Son, and is throughout, 

 especially in the tables and the catalogue, a beautiful piece of typo- 

 graphical work. 



PHOTOGRAPHY AS A MEANS OF CHARTING STARS. 



In a recent communication to the Paris Academy of Sciences, Ad- 

 miral Mouchez, director of the Paris Observatory, states that MM. 

 Henry, finding it almost impossible, on account of the great number of 

 stars, to chart the part of the heavens which they have now reached 

 by the methods heretofore adopted, have had recourse to photography. 

 Their first attempt with a provisional apparatus has been so successful 

 that Admiral Mouchez considers that the problem will soon be solved. 

 Proofs of jjlates taken with a telescope 0™.! in diameter and 2'".10 focal 



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