June i, 191 6] 



NATURE 



2%X 



A.D. 58 instead of a.d. 138, the alleged epoch. 

 The year a.d. 58 is 187 years after the epoch of 

 Hipparchus, which gives the amount of preces- 

 sion— 2° 36', agreeing closely with the difference 

 of 2° 40' found by Ptolemy. Mr. Knobel re- 

 marks that, as the correction could not represent 

 positions observed in a.d. 138, this supports the 

 view that the catalogue is simply that of Hij>- 

 parchus, with a constant amount added to the 

 longitudes. 



But this conclusion is by no means certain, 

 and was not accepted by Peters when he spoke 

 on this subject at the Kiel meeting of the 

 Astronomische Gesellschaft in 1887, less than 

 three years before his death. According to the 

 v^ry short report in the Vierteljahrsschrift 

 (xxii., p. 269), Peters said that the constant error 

 of the longitudes might very well be due to syste- 

 matic errors of Ptolemy's instruments or to faults 

 of the method (comparison of sun and stars with 

 the moon as an intermediary), neglect of re- 

 fraction, etc. The equinoxes of Ptolemy should 

 not be assumed to possess the accuracy required 

 to justify the above conclusion, and it would, in 

 fact, be remarkable if such accuracy had been 

 attained. Peters added that stars with large 

 proper motion, especially 40 Eridani, agreed 

 far better with the places of the stars at the time 

 of Ptolemy than with those at the time of Hip- 

 parchus. To these reasons for hesitating to 

 adopt the usual conclusion we would add the 

 common belief among the Arabs that Ptolemy 

 had borrowed his whole catalogue from Menelaus, 

 adding 25' {41 years' precession at 36") to the 

 longitudes. This seems in itself a far more 

 likely origin of the catalogue than that it should 

 have been borrowed from one made 270 years 

 earlier. But the problem of the origin of 

 Ptolemy's catalogue is still unsolved. 



J. L. E. D. 



PROF. H. C. JONBS. 

 ' I ''HE announcement in Nature of May 18 of the 

 -•■ death of Prof. Harry Jones, of Johns Hop- 

 kins University, will be received by his many 

 friends in this country with sincere regret, for his 

 transparent honesty and sincerity, his enthusiastic 

 nature, his kindliness, and his courtesy impressed 

 all with whom he came in contact. 



Harry Clary Jones was born in New London, 

 Maryland, in 1865, and received his academic 

 education in the famous university of his State. 

 He graduated as A.B. in i88g and as Ph.D. in 

 1892. The next two years he spent in Europe 

 working in the laboratories of Ostwald, Arrhenius, 

 and van't Hoff. Permeated with the ideas and 

 theories associated with these names, Jones re- 

 turned to America and proceeded to promulgate 

 them with boundless energy and enthusiasm. He 

 received an appointment on the teaching staff of 

 Johns Hopkins University, and was in time pro- 

 moted to the chair of physical chemistry. Jones 

 was a tireless worker himself and inspired his 

 numerous co-workers with an equal industry. 

 During the last twenty years he published, alone 



NO. 243 T, VOL. 97] 



and in conjunction with them, well above a 

 hundred papers, many of them memoirs of con- 

 siderable magnitude, and found time in addition 

 to write six books (text-books and semi-popular 

 works), several of which have passed through a 

 number of editions. 



The line of research to which he chiefly devoted 

 himself was the study of the intimate nature of 

 solutions. In the "ideal" solutions of van't Hoff 

 the mutual influence of solvent and solute may be 

 neglected. The main object of the investigations 

 of Jones and his fellow-workers w^as to ascertain 

 the nature and extent of this influence in actual 

 solutions. For aqueous solutions Mendeleeff had 

 advanced the hypothesis that the dissolved sub- 

 stance existed in the form of a hydrate or hydrates 

 of definite composition. Jones modified and ex- 

 tended this idea and held that dissolved substances 

 in general are combined with more or less of the 

 solvent as a series of solvates. To test this " sol- 

 vate theory of solution " his extensive experimental 

 work was devised. He explained abnormally low 

 freezing-points of concentrated solutions as due to 

 a portion of the solvent having combined with the 

 solute, so that the concentration in the remaining 

 solvent was greater than that deduced from the 

 composition of the solution, and showed that this 

 abnormality in aqueous solutions was greatest for 

 those substances which ' crystallise most readily 

 with water of crystallisation. By the use of the 

 grating spectroscope he showed that the absorption 

 bands of solutions became broader (i) as the solu- 

 tion became more concentrated, (2) as the tempera- 

 ture was raised, (3) as dehydrating substances were 

 added. In each case this would correspond to the 

 production of simpler hydrates. He also showed 

 that different absorption bands were obtained 

 according to the solvent in which the salts investi- 

 gated (chiefly those of neodymium, which give 

 sharp absorption bands) were dissolved, pointing 

 to the formation of different solvates. By means 

 of the radiomicrometer he demonstrated finally that 

 the water in concentrated solutions of non-absorb- 

 ing salts showed a smaller absorption in the infra- 

 red region than water itself. 



Of his text-books the " Elements of Physical 

 Chemistry " is deservedly the most successful, 

 being written in an easy, readable style, which 

 makes it popular with the student. In his " New: 

 Era in Chemistry " he described the progress of 

 the science from 1887 onwards, and struck a per- 

 sonal note which adds to the interest and pleasure 

 of perusal. J. W. 



NOTES. 



The Paris correspondent of the Times states that 

 the Committee of the Senate appointed to consider the 

 Daylight Saving Bill has reported against the measure 

 on the ground that the economy intended to be realised 

 IS doubtful, and that the change woulcT cause serious 

 inconvenience. 



In the recent debate on the Air Board in the House 

 of Lords several references were made to the scientific 

 side of aeronautics. This aspect of the subject is not 

 nearly so well known and appreciated as it should be 



