March i8, 1909] 



NA TURE 



indices of refraction at different parts of the spectrum of 

 substances possessing anomalous dispersion, and a dis- 

 cussion of the bearing of these observations on the theory 

 of dispersion of light ; experimental determinations, carried 

 out with the greatest care, of the atomic weight of at 

 least one element, the value of which is at present un- 

 certain ; a critical discussion of the theories of flight and 

 of the experimental researches which form the base of 

 such a discussion ; a theoretical and experimental examina- 

 tion of the causes of the deviations from Ostwald's dilution 

 law ; exact direct measurements of the osmotic pressure 

 of solutions, not showing electrolytic dissociation, especially 

 in view of the determination of the limit of concentration 

 at which the deviations from the laws of Boyle and Gay- 

 Lussac begin to be felt ; a research on the origin and 

 physiological signification of the green colouring matter 

 in the bodies of articulated green animals; an experimental 

 research on the electrolytic dissociation of substances dis- 

 solved in different mixtures of water and alcohol; a deter- 

 mination of the diminution of the vapour pressure of 

 solutions in water of the chlorides of sodium, potassium, 

 calcium, and magnesium between the temperatures o° C. 

 and 100° C. for at least six different concentrations, the 

 molecular conductivity, the lowering of the freezing point, 

 and the rise in the boiling point are to be determined for 

 the same solutions, the whole to be discussed from the 

 point of view of the theory of Arrhenius and the criticisms 

 of Kahlenberg ; a quantitative research on the radiation of 

 two simple gases in a magnetic field ; new quantitative 

 determinations on the distribution of radium in the earth's 

 crust : a study, as complete as possible, of the structure 

 and development of one species of the genus Trypano- 

 soma, Tr. h'wisi for preference. 



The gold medal of the society (or its value) is offered for 

 the best paper received in answer to one of these questions. 

 Replies should be written in Dutch, French, English, 

 German, or Latin, not signed by the author, but bearing 

 a motto, accompanied by a sealed letter containing the 

 same motto and the author's name, and addressed to Dr. 

 C J. W. Bremer, the secretary of the society, at Rotter- 

 dam, before February i, 1910. 



PAPERS AND REPORTS ON INSECTS. 

 Dt'LLETIN No. 3 of the Sleeping Sickness Bureau is 

 devoted to the life-liistory of the tsetse-fly, Glossina 

 palpalis, a species which appears to have been originally 

 obtained in Sierra Leone, but is now know'n to have a 

 very wide distribution, including Angola, Nigeria, the 

 Congo State, the lake region, the Egyptian Sudan, 

 Uganda, and north-eastern Rhodesia. After referring to 

 the peculiar mode of propagation of tsetses, "the author 

 discusses the influence of external conditions on the distri- 

 bution and numbers of the species under consideration, 

 referring particularly to shade, altitude, season, tempera- 

 ture and humidity, forest, water, and food-supply. 



.\ number of new species and one new genus of .American 

 mosquitoes are described by Messrs. H. C. Dyar and 

 F. Knab in vol. Hi. of the Smithsonian Miscellaneous 

 Collections, as a preliminary to a monograph now in course 

 of preparation by Dr. L. O. Howard and the authors of 

 this paper. The new genus, Dinanamesus, is allied to 

 Dinocerites, from which it differs by a reduction in the 

 length of the second joint of the antennre. 



In the report of the entomologist of the U.S. Depart- 

 ment of Agriculture for iqo8. Dr. L. O. Howard refers 

 to the work done during the year in connection with the 

 Mexican cotton-boll weevil, a species which continues to 

 inflict much damage on growing cotton. It has been 

 found that parasites are year by year becoming much more 

 effective in controlling the ravages of this weevil, a fact 

 promising favourable results in the efforts of the Bureau 

 to encourage and spread the former. During the season 

 under review the average parasitism is shown to have been 

 doubled in Texas and trebled in Louisiana. Special atten- 

 tion was also directed during the year to insects injurious 

 to forests, and it is satisfactory to learn that the efforts 

 of private owners and the forest officials to check and 

 control the alarming outbreaks of the' Black Hills beetle 

 in the neighbourhood of Palmer Lakes and Colorado 



NO. 2055, VOL. Sol 



Springs, as well as in the adjoining Pikes Peak National 

 Forest, have proved a complete success. 



The whole of vol. xxxi., No. 1, of Notes from the 

 Leyden Museum is devoted to a monograph, by Dr. H. W. 

 van der Weele, on the Mecoptera (scorpion-flies) and Plani- 

 pennia of " Insulinde." The latter name is taken to 

 denote the Dutch colonies in the Malay and Papuan archi- 

 pelagoes, but the paper, which is illustrated by five plates, 

 includes descriptions of species from those parts of Borneo 

 and New Guinea which do not belong to Holland. A 

 number of new species and subspecies, and three new: 

 genera, are named and described in the course of the 

 paper, while some interesting particulars are given with 

 regard to the Hfe-history of one of the species of " ant- 

 lion " (Myrmeleon). 



EXPLOSIVE COMBUSTION, WITH SPECIAL 

 REFERENCE TO THAT OF HYDRO- 

 CARBONS.' 

 T T is hardly necessary to remind you that the subject of 

 -'■ my discourse will be ever associated with the illus- 

 trious name of Davy. Davy turned his attention to the 

 phenomena of flame in the year 1815, in response to aiv 

 urgent appeal on the part of a committee formed in the> 

 north of England, to investigate the causes of accidents- 

 arising from the explosion of tire-damp in coal mines, and 

 to devise means for their prevention. The perennial 

 interest of his researches, however, lies not so much in 

 their immediate practical success, great as this undoubtedly 

 was, as in the broader theoretical issues which were dis- 

 closed, and brought within the region of experimental- 

 inquiry, by so splendid an exercise of genius. 



DaVy insisted on the necessity of considering flames in 

 all cases " as the combustion of an explosive mixture of 

 inflammable gas, or Vapour, and air," and he defined flame 

 as " aeriform, or gaseous matter, heated to such a degree 

 as to be luminous." For the starting and propagation of 

 a flame in an explosive mixture, he showed that each 

 successive layer of gas must be raised to a certain definite 

 temperature, called the " ignition point," and he investi- 

 gated both the ignition temperatures and' the explosion 

 limits of a large number of the commoner combustible- 

 gases. He then proceeded to his famous discovery that; 

 notwithstanding the extremely high temperatures of flames, 

 which, in the case of cyanogen, he estimated to be " above 

 5000° of Fahrenheit," they can be readily extinguished by. 

 contact with a cooling surface of sufficient area and heat- 

 conducting power, and that for this purpose metal surfaces 

 are by far the most efficient. How he developed anrf 

 applied this discovery to the construction of his " safe- 

 lamp " for miners is a matter of history. 



In experimenting upon the ignition temperatures of 

 explosive mixtures, Davy made the important observation 

 that combustible gases combine with oxygen at lower 

 temperatures without any appearance of flame whatever. 

 He emphasised the importance of a complete investigation 

 of the chemical aspects of this flameless combustion, and 

 he himself was led to ask whether, seeing that the 

 temperatures of flames far exceed those at which solids 

 become incandescent, a metallic wire can be raised^ to' 

 incandescence by the slow combustion of two gases " with- 

 out actual flame, but producing heat enough to keep the 

 wire ignited." In this way he discovered the remarkable, 

 property of platinum and other metallic wires of inducing 

 surface.' combustion, and in the course of his further experi- 

 ments on this subject he made two notable observations 

 respecting the burning of compounds containing carbon 

 and hvdrogen. He found " much carbonic oxide " pro- 

 duced 'when a platinum wire w-as kept incandescent, by 

 the slow combustion of a mixture of ethylene and o,xygen, 

 rendered non-explosive by an excess of the hydrocarbon., 

 and in a similar experiment with ether vapour he recorded 

 the appearance of " a pale phosphorescent light " accom- 

 panied by " the formation of a peculiar acrid, volatile 

 substance possessed of acid properties." 



Finallv. in speculating upon the difficult and thorny 

 subject of the luminosity of hydrocarbon flames, he \va>i 



' Ahridffed from a ,1i=co.ir=? ilelvered at the Royal Institution on Fiiday, 

 Febrar>- 2S, igoS, by Prof. W. A. Bone, F.R.S.. 



