262 



NATURE 



\ytdy II, 1889 



comprising several interesting points of construction and detail, 

 is at work at the Paris Exhibition. 



Mr, Deboutteville, in his paper, first reviews the gas-engines 

 hitherto proposed or employed. He carries back his researches 

 nearly a century, when the first gas-engine was proposed by 

 Barber, and completes them with a description of the Simplex 

 engine, which he brought out with Mr. Malandin in 1884. This 

 engine is founded on principles laid down by Mr. Beau de 

 Rochas — that, to realize the best results from the elastic force of 

 gas, the cylinders should have the greatest capacity with the 

 smallest circumferential surface, the speed should be as high as pos- 

 sible, the cut-off should be as early and the initial pressure as high 

 as possible. In the author's engine the ignition is effected by a 

 practically continuous electrical spark ; the air and gas are mixed 

 in an external receptacle fixed on the cover of the slide, and are 

 drawn in through channels of varied forms so as intimately to 

 mix them. The governors described act on the principle of 

 totally cutting off the supply of gas for one or more strokes 

 whenever an increase of speed occurs. From the tests made 

 with this engine the consumption of gas is low, and it appears to 

 compare favourably with good steam-engines as regards economy 

 of application. 



Besides the reading and discussion of papers, the members of 

 the Institution visited the Exhibition, and various works which 

 were opened for this purpose. 



SCIENTIFIC SERIALS. 



The numbers of the Jourtial of Botany for June and July aie 

 chiefly devoted to articles interesting to students of systematic or 

 geographical botany, especially that of our own islands ; the 

 latter number contains a biographical sketch of the late Prof. 

 Reichenbach, by the editor. 



The most interesting article in the Botanical Gazette for May 

 is the commencement of a detailed paper by Mr. C. Robertson, 

 •on the relations between insects and flowers in regard to American 

 plants. The number for June contains original articles by Mr. 

 H. L. BoUey, on sub-epidermal rusts, and by Mr. J. N. Rose, on 

 the Achenia of Coreopsis. 



The American Meteorological Journal for May contains 

 abstracts of the papers read at the meeting of the New England 

 Meteorological Society on April 16 : — In a paper on lightning 

 and the electricity of the atmosphere, Mr. McAdie gave an 

 account of some kite experiments at the Blue Hill Observatory, 

 near Boston, in which the potential was determined at various 

 heights. He also referred to the observations on the character 

 of lightning at the top of Mount Washington during thunder- 

 storms, and to the effect of the electrification of the air upon 

 water, dust, and other particles in it, and to the possibility of 

 foretelling the moment of a flash of lightning. — Prof. W. M. 

 Davis made a report upon the investigation of the sea-breeze, 

 undertaken in 1887, from observations at lOO stations. One 

 fact shown was that the diurnal range of temperature, which is 

 diminished on the coast by the action of the sea-breeze, is not 

 lessened at the inland stations. — Mr. E. B. Weston read a 

 paper on the practical value of self-recording rain-gauges, 

 referring to the importance of knowing the hourly falls when 

 constructing drainage systems. — Prof. H. A. Hazen continues 

 the discussion upon anemometer comparisons, and upon the 

 question of the probable effect of the momentum of heavy 

 cups, when placed on a whirling machine. He considers that 

 the Robinson anemometer is by far the best instrument ever 

 devised for variable winds. — Lieut. Finley discusses the frequency 

 of tornadoes in Illinois for fifty-four years, ending with 1888. 

 The total number of storms was 141. The month of greatest 

 frequency was May, no month being free from storms. The pre- 

 vailing direction of movement was north-east. — Prof. Harrington 

 communicates the instructions issued by the Chief Signal Officer 

 for the preparation of forecasts and for their verification. The 

 instructions contain nearly 200 regulations, and are very interest- 

 ing to those who study weather predictions. 



The Meteorologische Zeitschrift (Vienna) for June contains the 

 first part of an epitome of Dr. von Bezold's papers on the thermo- 

 dynamics of the atmosphere, which have already been summarized 

 in our notices of Societies. — Dr. J. Hann contributes a valuable 

 article on the results of the meteorological observations of the 

 late Prof. A. Ackermann at Port-au-Prince, Hayti, 1854-68, 

 being a part of the world where they are of special value. The 



observations were rescued from entire loss by the exertions of 

 Dr. Hann and Prof. J. Scherer, the originals having been 

 wilfully destroyed. The distribution of rainfall is much affected 

 by the mountain features of the island ; in the north the rainy 

 season is from December to April, while in the south it is from 

 May to July. The average yearly rainfall at Port-au-Prince, 

 from the above observations, was 61 inches, on 153 days. The 

 greatest daily fall was 5 "6 inches in May 1865, the rain lasting 

 four hours. The climate is very equable ; the mean of the 

 absolute maximum temperatures was 98° "2, and of the minimum 

 56°'8. — Dr. von Lepel describes his experiments in passing 

 electric sparks through glass tubes lined with a thin coating of 

 paraffin, and containing a small amount of moisture, and points 

 out that during thunderstorms many similar discharges may be 

 observed, and may find their explanation in these experiments. 

 The sparks differ in character and in colour, and the author 

 argues that the humidity in the tube may be compared to the 

 particles of vapour in the thunder-clouds, and that the coating 

 of paraffin may have the same optical effect as the translucent 

 clouds themselves. He gives the results of his thunderstorm 

 observations on these lines during the summer of the year 1888. 



SOCIETIES AND ACADEMIES. 



London. 

 Physical Society, June 22. — Prof. Reinold, F. R.S., 

 President, in the chair. — The following communications were 

 made : — Note on some photographs of lightning, and of 

 "black" electric sparks, by Mr. A. W. Clayden, The light- 

 ning photographs, three in number, were obtained during the 

 storm on June 6. Two flashes, seen on one plate, show com- 

 plicated and beautiful structure : one of them is a multiple flash, 

 and flame-like appendages point upwards from every angle ; the 

 other is a broad ribbon, and, although the plate shows signs of 

 movement, the displacement is not in a direction such as would 

 produce a ribbon-like effect from a linear flash. The second 

 plate shows four flashes, none of which are ribbon-like, though 

 the camera had moved considerably. The third plate was ex- 

 posed to six flashes, one of which was believed to pass down 

 the middle of the plate ; but, on development, only a triple flash 

 in one corner of the plate was seen. Careful search, however, 

 revealed the central flash as a dark one with a white core, and 

 other dark flashes were subsequently found. The plate was 

 very much over-exposed, and this suggested that black flashes 

 might be due to a sort of cumulative action caused by the super- 

 position of the glare from a white cloud upon the normal image 

 of the flash. To test this, sparks from a Wimshurst machine 

 were photographed, and, Ijefore development, the plates were 

 exposed to diffused gas-light for a short time. The bright sparks 

 yielded normal images wiih reversed margins, and the faint ones 

 were completely reversed. Other experiments showed the re- 

 versal to spread inwards as the time of exposure to gas-light 

 increased. Finally, reversal was effected by placing a white 

 screen behind the spark, to represent a white cloud, the only 

 illumination being that of the spark itself. In the discussion 

 which followed, Mr. W. N. Shaw exhibited a photograph taken 

 during the same storm, which is particularly rich in dark flashes 

 branching outwards from an intensely bright one. In some 

 places the bright line has dark edges, and in one part a thin 

 bright line runs along the middle of an otherwise dark portion 

 of the flash. In answer to Mr. Inwards, Mr. Shaw said the plate 

 was exposed about half a minute, and the former thought that, 

 under those conditions, the appearance of the plate did not con- 

 tradict Mr. Clayden's hypothesis. Speaking of the same pho- 

 tograph, Prof. Perry considered that Mr. Clayden's observations 

 would explain the result, for a bright flash required more ex- 

 posure to diffused light to reverse it than a faint one did. Prof. 

 Ramsay reminded the meeting that Prof. Stokes's "oxides of 

 nitrogen " explanation was still a possible one ; and Mr. C. V. 

 Burton asked whether they may be due to faiat sparks cutting 

 off light from brightly illuminated clouds, just as a gas-flame 

 absorbs light from a brighter source. In reply, Mr. Clayden 

 thought the "oxides of nitrogen" hypothesis improbable, and 

 said his experiments did not enable him to answer Mr. Burton's 

 question. As regards Mr. Shaw's plate, he believed the diffused 

 light from the clouds would be sufficient to reverse the fainter 

 tributary flashes, although it was insufficient to reverse the 

 primary one. From data obtained when the ribbon-flash was 

 taken, he had made some calculations which gave the height of 

 the clouds about loco yards, and the ribbon-flash 1300 yards 



