April 12, 1894] 



NA TURE 



561 



■e ■\- X -^ tv = JQ. Hence, since e = JQ, x — ~ iv. On the 

 other hand, if we consider the disc and field magr.ets as forming 

 the system under consideration, tlien lu = JQ, and therefore 

 i = — zv. Since, therefore, the work done by the electro- 

 magnetic forces, in the case of the turning disc, is not zero, 

 while the induced currents remain at rest with regard to the 

 field magnets, the point of application of the electromagnetic 

 forces must be the matter conveying the currents, and not the 

 current itself, as the faulty reasoning in the previous paper in- 

 ■dicated. 



During 1893 a number of British agriculturists visited 

 Canada, with a view to report uoon the agricultural resources 

 of the country. Among these visitors were Profs. James Long 

 and Robert Wallace, and the reports prepared by these 

 gentlemen have just been published. With the object of seeing 

 exactly what is done by the Gavernment for the benefit of the 

 farmer, Prof. Long visited three of the fiwe experimental farms 

 which are now in full working order in the Dominion — those of 

 Ottawa, Brandon, and Indian Head. The Ottawa farm is some 

 •five hundred acres in extent, and the reports of the experi- 

 mental work done in it are sent to 25,000 farmers. The 

 Manitoba experimental farm consists of 625 acres of land, in 

 which a large number of valuable tests of grain suited to the 

 country have been carried out. The experimental farm at 

 Indian Head cavers 680 acres. These farms are of the utmost 

 importance to agriculturists. Hundreds of experiments are 

 made in them with cereah, i>ulse, grasses, fruits, vegetables, 

 forest trees, and plants of other kinds, with the object of pro- 

 viding the farmer with the best seed or the best v.iriety. Some 

 day, perhaps, our Government will promote the prosperity of 

 agricultural interests in the British Islands, by establishing 

 and endowing similar experimental stations here. 



The members of the London Geological Field Class will 

 visit Wanborough and Guildford on Saturday, April 21, under 

 the direction of Prof. H. G. Seeley, F.R.S. 



Messrs. Blackie and Son have issued a guide to the 

 Science and Art Department examinations in heat, and one to 

 the examinations in hygiene. Both books contain answers to 

 questions set from 1886 to 1893, inclusive. 



The " Handbook of Tasmania" for the year 1893, has been 

 received. It contains a large amount of important statisticil 

 information referring to the colony, and a brief epitome of the 

 historical portion of the " Tasmanian Official Record," which 

 will in future be issued iri-annually instead of annually. 



The April volume of The Country Month by Month (Biiss, 

 Sands, and Foster) should be obtained by all ramblers through 

 ■"meadows pied" and over " hillsides breaking; in blossom," 

 during this month. The book is brightly written by Mrs. J. A. 

 Owen and Prof. G. S. Boulger, and forms a mjst interesting 

 •companion for country walks. 



The scientific publications of the Government of South Aus- 

 tralia are very much in arrears. We have only just received 

 the volume of meteorological observations made at the Ade- 

 laide Observatory and other places in South Australia and the 

 northern territory, during the years 1886 7, under the direction 

 of Sir Charles Todd, C.M.G., F.R.S. 



The Camera Club Conference will be opened by Captain 

 Abney, at the Society of Arts, on Monday, April 23. Among 

 the papers down for reading on the following day is one by Prof. 

 'W. Rober;s-Austen '^ On the Methods of Recording High Tem- 

 peratures by the Aid of Photogi-aphy." Mr. A. Mallock will 

 treat of "The Amount of Photographic Action Produced by 

 Various Lengths of Exposure and Intensities of Light," and 

 Mr. Andrew Pringle on " The Keeping Qualities of the Modern 

 IDry^late." 



NO. 1276, VOL. 49] 



The Join nal o{ [.he Royal Statistical Society for March con- 

 tains an important and comprehensive paper (the Howard Medal 

 Prize Essay) on " The Perils and Protection of Infant Life," 

 by Dr. Hugh R. Jones. The author concludes by saying : " I 

 have insisted that the preventable forms of child neglect are in 

 the main referable to want of parental responsibility — a con- 

 dition which, it is certain, largely depends on ignorance. The 

 remedy — the only remedy — in which I have any faith or 

 confidence, is education." 



The report of Mr. C. Meldrum, the Director of the Royal 

 Alfred Observatory, for the year 1892 has recently been issued. 

 Though the work of the observatory refers chiefly to meteoro- 

 logy and terrestrial magnetism, a very useful part of it belongs 

 to astronomical physics, for photographs of the sun are taken 

 every day, when the weather permits. During 1892, 303 solar 

 negatives and 285 prints were forwarded to the Solar Physics 

 Committee for reduction. Records were obtained of well- 

 marked magnetic disturbances on the following dates : — 

 January 4-5, February 13-15 (this was the disturbance which 

 accompanied the great sun-spot of February 1892), March 6- 

 7, March 12 13, April 25-27, May 18-20, June 27-29, July 

 12-14, Ju'y 16-17, August 12-13, September 13, and De- 

 cember 5-6. 



The Royal Meteorological Society and the Sanitary Institute 

 have arranged a course of lectures on meteorology in relation to 

 hygiene, to be given in the Parkes Museum on Mondays and Thurs- 

 days, from April 23 to May 10. Mr. G. J. Symons, F.R.S., will 

 begin the course with a lecture on "Instruments and Observa- 

 tions and their Representation." He will be followed by Dr. 

 H. R. Mill on the "Temperature of Air, Soil, and Water.' 

 Mr. R. H. Scott, F.R.S., will lecture on "Barometric Con- 

 ditions and Air Movements " ; Mr. W. Marriott on " Moisture, 

 its Determination and Measurement " ; Dr. C. Theodore 

 Williams on " Climate in Relation to Health, and Geographical 

 Distribution of Disease " ; and Mr. F, Gaster on " Fog, Clouds, 

 and Sunshine."' 



We have received from Messrs. O. Newmann and Co. a 

 copy of a small book, devised and arranged after the directions 

 of Dr. H. Zwick, on "Optical Experiments." In it are de- 

 scribed a series of 150 experiments illustrating the laws of the 

 propagation, reflection, and refraction of light. To make this 

 course more useful to the class of student for which it is speci- 

 ally intended, namely beginners, the apparatus chosen is of a 

 simple kind. The light source adopted throughout is that of a 

 candle, and the experiments are selected accordingly. All the 

 instruments referred to in the text are stated to be perfectly 

 trustworthy, and the experiments are arranged for class-work 

 so that many scholars may view them at the same time. For 

 those wishing to occupy them;elves with the more simple 

 physical experiments, the book will be a useful guide. The 

 descriptions of the ex leriments would perhaps have been 

 improved if some of the technical terms employed had been more 

 fully defined ; for instance, in the first experiment the be- 

 ginner is introduced to the words "rectilineal transmission," 

 "translucent," &c. In the preface, however. Dr. Zwick refers 

 the reader, concerning the headings, to any good text-book of 

 natural philoso^jhy, th is restricting himself solely to the descrip- 

 tion of the experiments. Numerous diagramsaccompany thetext. 



At the Institution of Civil Engineers, on April 3, Mr. C. 

 Hunt gave some interesting particulars with regard to the 

 manufacture of gas. It has been generally assumed that the 

 deficient yield of tar which usually acco npanied the use of a 

 high carbonising temperature is fully made up by increased 

 production of gas. In Mr. Hunt's experience, however, the 

 highest production of gas has been accompanied by the largest 

 yield, both of tar and ammoniated liquor. Experiments have 



