210 



KNOWLEDGE 



[Septembeb, 1908. 



Contributions to Knowledge. 1903.) — This valuable memoir is 

 a continuation of the "U.S. Weather Bureau, Bulletin 12" 

 (18'.I3), and of the " Smithsonian Contributions to Knowledge," 

 Vol. XXIX. (1901), by the same author, and but for a little 

 ])refatory "advertisement" by Prof. Langley it would be very 

 difficult for the reader to understand Prof. Barus' present 

 researches without a careful study "of the previous works. Even 

 as it is, it is much to be regretted that Prof. Barus has not 

 given a concise summary of the objects, methods and results of 

 the two previous papers ; and especially has not clearly defined 

 both " nucleus " and " corona,'' and given a description or 

 representation of some of the forms of the latter. Apparently 

 nuclei are extremely small particles tending to precipitate water 

 from moist air, when this is suddenly cooled, and in the present 

 researches they were usually supplied by introducing into the 

 receiver air which had passed over phosphorus, or burning 

 sulphur, or glowing charcoal. They could be obtained, how- 

 ever, without putting anything material into the receiver, by 

 passing the X-rays or other form of radiation through it. Here 

 the production of nuclei in case of weak radiation is very 

 gradual, and it takes time to produce them, but when once 

 produced they show a degree of persistence identical with that 

 of nuclei of any other origin. Since there is no qualitative 

 difference referable to their origin, the stuff out of which their 

 nuclei are made must be in the gaseous contents of the receiver 

 (air or vapour). The chief aim of the memoir is to throw light on 

 the phenomena connected with the presence of nuclei in air by 

 aid of the " coronas " or colour rings seen in such air where its 

 moisture is condensed and deposited on the nuclei, and a distant 

 source of light is looked at through the turbid medium. The 

 author accepts the theory that nuclei which vanish are absorbed 

 on contact with the walls of the vessel, and that no other loss 

 of nuclei occurs. Nuclei are sparsely distributed (10- to 10" per 

 cub. cm.) in comparison with molecules. In using an emana- 

 tion of phosphorus as an ionizer, the author found incidentally 

 that, under certain conditions, the emanation produced per- 

 manent conduction in the condenser. This he identified with 

 the occurrence of traces of moisture, but the behaviour so closely 

 resembled the effects of radio-activity, that he concluded that 

 the latter quality could only be predicated with extreme caution. 



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Memoirs of the British Astronomicl Association. Fifth Report 

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The Crotod. By Gustare le Bon. (Fisher Unwin.) 63. 



Suddhist India. By T. W. Rhys Davids, LL.n., PH.D. (Fisher 

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Fundamental Problems. By Dr. Paul Carus. (Kegan Paul.) 7b. 6d. 



Position of the Old Red Sandstone in the Geological Succession. 

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School Geomelri/. Part III. By H. S. Hall, it. A., and F. H. 

 Stevens, M.A. (Macmillan.) Is. 



Smithsonian Institution. Report of the U.S. National Museum 

 for the Year ending June 30th, 1000. (Washington : Government 

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Smithsonian Institution. List of Publivaf ions, 1S46-1903. 



Doubts about Danoinism. By a Semi-Darwinian. (Longmans.) 

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Elementary Chemistry of Photographic Chemicals. By C. Sordes 

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Catalogue of 1520 Bright Stars. (Cambridge Observatory, Mass.) 



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THE VATICAN OBSERVATORY. 



By W. Alfred Pare. 



When towards the middle of the niutli century Pope 

 Leo. IV. sought to stem the further ravages of the 

 Saracen hordes bv strengthening the defences of Rome 

 and enclosing the Vati('an hill with massive turreted walls, 

 he could little imagine that these same walls, designed so 

 well to bear the engines of war that were to dominat« the 

 country round, would, more than a thousand years later, 

 be required by a successor and namesake to harbour a 

 weapon of science of a potency little dreamt of in those 

 days — a weapon whose range of power should penetrate to 

 the confines of the unknown itself. For, after the 

 conclusion of the International Photographic Conference 

 on the charting of the heavens, held in Paris in 1889, it 

 was on one of the strongest of the towers forming part of 

 the ancient Leonine wall that the late Pontiff, Leo XIII., 

 decided to erect the newly-ordered astrographic telescope 

 which was to enable the Vatican Observatory, until that 

 time somewhat meagrely equipped, to worthily enter the 

 lists with the seventeen other observatories to whom the 

 work of the chart had been allotted. 



The history of the Vatican Observatory is no less 

 interesting than varied. Closely associated in its earliest 

 years with one of the most memorable achievements in the 

 annals of mathematical science — the reform of the calendar 

 in 1582, under Gregory XIII. - it was shortly afterwards 

 suffered to lapse into complete neglect for neaidy a century 

 and a half. Gregory, however, may be said to have 

 founded the observatory when he erected that lofty portion 

 of the Vatican Palace known as the " Torre dei Venli," 

 not, as some rather uncharitably maintained, in order 

 merely to enjoy the e.\tended view obtainable from its 

 summit, but in order to institute the study of celestial 

 phenomena in general. That the latter purpose was the 

 true one seems amply evidenced by the tower being referred 

 to in the inscriptions as the " turris astrorum speculatrix," 

 and by the fact that it contained the meridian line, 

 constructed to demonstrate to Gregory that, in his time, 



