December 24, 190S] 



NA TURE 



number of the Bulletin of the Academy of Science of 

 Cracow a theory which will at the least serve as a good 

 worlving hypothesis. It is based on the corpuscular theory 

 of matter, and assumes that amongst the systems of 

 electrons which constitute the atoms and molecules, there 

 are a number in a state such that a small increment of 

 energy will render them unstable, and one or more 

 electrons will be shot out of the system. These are in 

 turn supposed to enter systems in which the electrons are 

 capable of executing oscillations without becoming un- 

 stiblc. It is these electrons which give out the fluorescent 

 lii^lit when the former systems are rendered unstable by 

 the incidence of radiation on them. The author shows that 

 ibis theory is in keeping with the known facts of 

 llunrescence and phosphorescence. 



Messrs. Leitz and Co. have put on the market a 

 universal projection apparatus designed in accordance with 

 th' suggestions of Prof. Kaiserling. We have examined 

 iliis apparatus, and find it most complete. It is avail- 

 able for projection on the screen under a variety of con- 

 ditions, viz. by transmitted light for both lantern and 

 microscopical work, and by incident light for the projec- 

 tion of woodcuts and natural objects. The special feature 

 (if the design consists in the ease with which the change 

 can be made from one mode of projection to another. 

 For episcopic projection it is arranged that the object 

 may either lie horizontally on the table or be in a vertical 

 position. Thus, if it be desired to project on the screen 

 part of a hospital patient, the subject is simply placed at 

 tbi- side so that the part in question may be illuminated 

 ])> the lamp and completely reflected by the mirror. The 

 electric lamp employed is one of the type which this firm 

 is adapting to several purposes. The carbons are at right 

 angles to one another, the positive one being horizontal 

 and lying along the optic axis. With this arrangement 

 the full crater becomes operative in producing useful light. 

 Tlie result is considerably greater efficiency, a power of 

 10.500 candles being obtainable with a current of 

 30 amperes. It is unnecessary to state that the optical part 

 possesses the excellence of this firm's work. The lantern 

 condenser is sufficiently large to illuminate a half-plale 

 transparency, and the whole of it can be simultaneously 

 projected on the screen. For microscopic projection both 

 objectives and projection eye-pieces are quickly changed by 

 revolving carriers. For the lower power objectives the 

 entire field is in focus at once ; it is only in the case of 

 I he diflicult projection with i/i2th inch (oil immersion) 

 ihat the peripheral regions are blurred. At present there 

 i- no polarising device, but this is under design. The 

 'iitire apparatus stands inside a curtained frame, which 

 prevents the escape of light into the room except through 

 the lens. It stands on the floor, with the optic axis about 

 144 cm. from it. 



Hazell's -Annual for 1909 has been received. The 

 volume includes much information of scientific interest, 

 and is a valuable, concise record of progress in many 

 departments of intellectual, industrial, and social activity. 



Messrs. Siemens Brothers and Co., Ltd., have issued 

 a convenient self-opening pocket diary for 1909. In addi- 

 linn to the usual calendar notes and diary, the book con- 

 I lins useful tables and illustrations of various dynamos 

 ind other machines made by Messrs. Siemens. 



In an article in the Johns Hopkins Hospital Bulletin 



for November, Dr. Peyton Rous describes the course of 



physiological pathology which is given in the school of 



medicine of the University of Michigan. It extends over 



NO. 204,-!. VOL. 79] 



three hours a day during three weeks, and includes the 

 pathology of vascular, cardiac, and respiratory disturb- 

 ances. 



The fourth quarterly bulletin, for the year 1906—7, of 

 the results obtained during the periodic cruises and in the 

 intermediate periods, has been issued by the Conseil per- 

 manent international pour 1 'Exploration de la Mer. The 

 bulletin deals with the following points : — condition of the 

 atmosphere ; the temperature and salinity of the surface 

 water ; the temperature, salinity, density, &c., of sea- 

 water at different depths ; oxygen, nitrogen, and carbon 

 dioxide dissolved in sea-water ; and plankton. The 

 bulletin is published by Messrs. A. F. H05t and Son. of 

 Copenhagen. 



The recent address delivered by Mr. Rudyard Kipling 

 to the students of the medical school of the Middlesex 

 Hospital, at the opening of the present session, has been 

 published by Messrs. Macmillan and Co., Ltd., in the form 

 of a booklet bound in limp cloth, at the price of \s. net. 

 The title of the little book is " Doctors," and, in addition 

 to the address, the book contains as frontispiece a photo- 

 I graph of Mr. Kipling and a preface describing the work of 

 the hospital, written by Mr. Reginald Lucas. We notice 

 that the book is being sold for the benefit of the Middlesex 

 Hospital. 



The 1909 number of " Whitaker's Almanac " is the 

 forty-first annual issue. It is difficult to imagine what one 

 would do without this indispensable book of reference, 

 which has again increased in size and usefulness. Among 

 new articles which have been included we notice those 

 dealing with the navigation of the air and the radio- 

 telegraphic convention, while the following interesting 

 features will continue to appeal to students of science : — ■ 

 progress of astronomical science, the year's weather in 

 the British Isles, the storms and floods of the year, and 

 the earthquakes and volcanic eruptions, the year being in 

 each case that ending on October 31, 1908. 



OVR ASTRONOMICAL COLUMN. 



Morehouse's Comet, igoSc. — A further discussion of 

 the photographs of Morehouse's comet, taken at Juvisy, 

 is published bv M. Flammarion in the December number 

 of the Bulletin dc la Societe astronomique de France 



(P- 513)- 



M. Flammarion reproduces further photographs, and 

 shows that, while the main features of the tail are ex- 

 plicable by the Maxwell-Bartoli laws of light-pressure 

 demonstrated experimentally by Lebedew, there are other 

 features which point distinctly to the operation of other 

 causes. For example, the photograph of October 15 shows 

 the now well-known dislocation of the tail, at some 

 distance from the head, which might be due to the inter- 

 ference of meteoritic matter. On the photograph _ of 

 October 17, however, there is no definite dislocation, 

 although there is distinct evidence that the tail, as_ a 

 whole, suffered some retardation in respect to the motion 

 of the nucleus. Several possible explanations are offered, 

 with full reserve, for this phenomenon. One is that the 

 aether mav have a density which is not homogeneous ; 

 another is' that the sun is constantly repelling matter into 

 interplanetary space, and that this matter would retard 

 the masses 'of tenuous vapours forming the tail of the 

 comet. A third explanation is that most generally 

 accepted, viz. that the retardations and dislocations are 

 probably caused by the interference of masses of meteorites 

 with which space is probably peopled. 



A note in the same journal (p. 534) announces that 

 MM. le Comte de la Baume Pluvinel and Baldet have, 

 since the publication of their preliminary paper in the 

 Coinptcs rcndns, obtained many more photographs of the 



