6i4 



NATURE 



[April 27, 1899 



cases the pollinating insects make their way at once to the 

 flowers which contain the honey, without being visibly guided 

 by the showy organs in either case ; while, if these are removed, 

 it does not appear to make any material difference in the 

 number of insects which visit the inflorescence. 



The conception of vast magnitudes forms the basis of two 

 papers in Die Na/iir for April, by H. Sonnenschmidt, entitled 

 " A Glance at the Kingdom of Large Numbers." 



" MosQUiTOS AND Mai.aria " form the basis of an article by 

 Dr. F. Mesnil, in the Revue gim'rale des Sciences, on the 

 h.xmatozoa of marsh fevers. The paper is illustrated by figures 

 showing the different stages of the hxmatozoa both of man and 

 of birds. 



Lv two papers communicated to the Verhaiidluitgen of the 

 German Physical Society, C. Liebenow applies the principles 

 of thermodynamics to calculate the thermo-electromotive force of 

 metal conductors, and compares the results of theory and 

 experiment. 



The Horseless Age, a New York journal devoted to the interest 

 of the motor vehicle industry, is now, at the beginning of its 

 fourth year, issued weekly instead of monthly. The first number 

 of the new volume contains a paper by Mr. Hudson Maxim, on 

 "Some thermodynamics of vehicle motors," and an editorial 

 discussion on the question "Shall vehicle motormen be 

 licensed ?" 



An extension of the methods of integration of Monge and 

 Ampere is worked out by G. Vivanti in the Rendicottii del R. 

 Istituto Lomhardo, xxxii. 6. The present paper contains a 

 generalisation for any number of variables of certain investiga 

 tions of the types of partial differential equations of the second 

 order which satisfy conditions of integrability, the correspond- 

 ing system of conditions in the case of three variables having 

 been investigated previously by \ivanti, whose results have been 

 generalised by Forsyth. 



In a communication to the Bulletin of the Cracow Academy 

 No. 2, M. K. Zorawski applies the method of conformal repre- 

 sentation to the convergency of Lagrange's, Blirmann's, Hoene- 

 Wronski's, and other series derivable from Taylor's theorem. 

 The same writer also discusses the geometry of certain infinites- 

 imal transformations and differential expressions which do not 

 possess the property of remaining invariable under the given 

 transformations. This number of the Bulletin also contains 

 papers by S. Kepinski on the integrals of solutions of certain 

 equations of the second order with three singular points. 



In Terrestrial Magnetism for March 1899, Dr. L. A. Bauer 

 gives two papers, one on the physical decomposition of the 

 earth's permanent magnetic field, and the other a preliminary 

 note on the question, "Is the principal source of the secular 

 variation of the earth's magnetism within or without the earth's 

 crust ? " The object of the first paper is to resolve the earth's so- 

 called permanent field into component ones physically inler- 

 pretable. In it the author arrives at the somewhat striking 

 conclusion that the unsymmetrical distribution of the earth's 

 magnetism, and the unsymmetrical distribution of temperature as 

 exhibited on the earth's surface, on the average for the year, are 

 in some way related to each other. 



Prok. II. PoiNCARI^:, writing in the Re7.'uc genirale des 

 Sciences, deals with certain considerations connected with the 

 theory of prolrability. The author, from consideration of various 

 problems, points out thai in all probability calculations it is 

 necessary to take as starting-point some hypothesis or conven- 

 tion which is always to a certain degree arbitrary. The most 

 frec|ucnt hypothesis is the doctrine of continuity, and the most 

 NO. 1539. VOL. 59] 



satisfactory calculations are those in which the result is inde- 

 pendent of the hypothesis made at the commencement, provided 

 that this hypothesis satisfies the conditions of continuity. 



Dr. H. J. OosTlN-c, writing in the Zeitschrift fiirdcn physikal- 

 ischen undchetnischen Unterricht, describes several contrivances 

 for exhibiting the resultant of two circular or elliptic vibrations of 

 different periods. In these a beam of light is reflected in suc- 

 cession from two mirrors, which are made to rotate about axes 

 nearly but not quite perpendicular to their planes, the two 

 rotating systems being connected by cogged wheels or an end- 

 less band, by which the ratio of the periods of rotation i.i 

 defined, and the path of the resultant motion is shown by 

 allowing the doubly-reflected beam to fajl on a screen. The 

 curves produced by composition of two circular or elliptic 

 motions could be drawn by a much simpler apparatus, consisting 

 essentially of a jointed pendulum capable of vibrating in al) 

 directions; but we would suggest that Dr. Costing's method 

 might be applied to tracing the various forms obtained by com- 

 pounding three or more circular motions whose periods are in 

 the ratio of different whole numbers. 



Slowly but surely the photographic film is taking the place 

 of the glass plate for many purposes, and its introduction now 

 into the physical and astronomical laboratory is an important 

 indication of its progress. Being light and flexible, and as 

 sensitive and durable as glass plates, the two first-named 

 properties render it of great service where weight and curved 

 fields have to be dealt with. To determine the value of films 

 where it is difiicult to use the ordinary glass plate. Sir Norman 

 Lockyer has lately been experimenting, and ver)' successfully, 

 with them, with the idea of adapting them to spectroscopic photo- 

 graphy. The large concave Rowland grating now in use for solar 

 spectroscopic photographs, has 20,000 lines to the inch ruled on 

 its surface, and isof 21.J1 feet radius, 'giving a spectrum of 30 inches 

 long. The focal plane of this grating is of necessity considerably 

 curved ; in fact, the jilane of accurate definition at the edges of 

 the field is about 05 inch in front of the similar plane at the 

 centre. It is, therefore, impossible to get a sharp photograph 

 of the whole spectrum on a glass plate ; in fact, not more than 

 18 to 20 inches of the spectrum can be brought into focus on 

 the same plane. This difficulty is, of course, got over by the 

 use of a flexible film, which can be bent to the curvature of the 

 field. The Kodak Company have sent us a print of one of Sir 

 Norman's photographs taken with this Rowland concave 

 grating. It is 30 inches long, and shows the arc spectrum of 

 iron with a comparison spectrum of the sun from wave-length 

 3600 to 5200, and the lines are beautifully sharp from one end 

 to the other. Sir Norman Lockyer also hopes that by using 

 films, instead of glass plates, at the next solar eclipse, he will 

 be able to obtain a greatly increased number of photographs, 

 owing to the rapidity with which the film can be shifted in the 

 short space of time available for photographic operations. At 

 the last eclipse the photographic work was concentrated on ob- 

 taining a series of ]ihotographs of the chromosphere, both about 

 the time of beginning and end of totality. By careful drill Mr. 

 Fowler and Dr. \V. j. S. Lockyer were both able to secure ten 

 photographs at each of these important periods, the lime 

 occupied in making each series of ten exposures being twelve 

 seconds. An apparatus for carrying films is also being designed, 

 which can be adapted to the spectroscopic cameras at present in 

 use in the laboratory and observatory. 



At the recent meeting of the Institution of Mining Engineers, 

 the use of highprevsure steam as a possible substitute for gun- 

 powder or other dangerous explosives in coal mining was 

 suggested by Major-t^'ieneral H. Schaw, C.B. Broadly, the sug- 

 gestion is that a cartriilge of pure water lodged in a shot-hole 



