598 



NATURE 



[October 19, 1891 



dependent on the labours of English seamen for their sailing 

 directions, they now rely almost entirely on their own publica- 

 tions, except as regards nautical charts. Dr. Schott gives an 

 intelligible account of the older or circular theory of storms, and 

 of the later, or spiral theory, to which attention was drawn by 

 Dr. Meldruin, in i860. If the former theory be correct, a ship 

 which in a given position might safely run across the path of an 

 advancing storm, would according to the later theory run into 

 the most dangerous part of it. Between these theories seamen 

 must therefore have great difficulty in shaping a correct course 

 at the most critical time, and every careful inve^jtigation into 

 the movements and laws of storms should be welcomed, in the 

 interest of science, whether undertaken by this country or by 

 foreign nations. 



In connection with the science meetings at the Chicago Exhi- 

 bition, Dr. M. A. Veeder read a paper on periodic and non- 

 periodic fluctuations in the latitude of storm tracks, in which he 

 referred to the occasional rearrangements in the distribution of 

 the atmosphere, consisting, in the main, in the displacement of 

 the belts of high pressure on each side of the equator, with the 

 consequent deflection northward or southward of the usual 

 courses taken by storms. Notable instances of this kind have 

 occurred at diff'erent times, such as in 1877-8 and in 1888-9, 

 and the present year also affords another example, the winter 

 in northern latitudes being distinguished by a severity in strong 

 contrast to their mildness during the years above mentioned. 

 These rearrangements of weather conditions on a large scale 

 make it difficult, the author considers, to resist the conclusion 

 that the atmosphere as a whole is under the control of forces 

 which have a common origin, and depending upon some form of 

 solar variability. Although it is not yet beyond dispute whether 

 the sun is hottest or coldest when most free from spots, the 

 evidence appears conclusive that the weather conditions in 

 question bear some sort of relation to thespottedness of the sun. 

 The author thinks that there is ground for the belief that there 

 may be special forms of solar activity not yet fully understood, 

 which exercise powerful terrestrial effects independently of the 

 amount of solar heat falling upon the earth as a whole, and 

 which may be of the nature of electro-magnetic induction, and 

 depend upon conditions different from those which appear in the 

 case of simple radiation from a source of combustion. If the 

 variation in weather types follow the solar electro-magnetic 

 record, he thinks that it would not be unwise to approach the 

 problems from this side of the question, although it would 

 involve a reconsideration of the facts of meteorological science 

 from a standpoint different from that of an assumed variability 

 of solar heat. The author considers that it may be necessary 

 o discard provisionally the accepted theory of the origin of 

 storms, in order to determine the part which electro-magnetic 

 induction of solar origin plays, independently of heating 

 effects. In any case, the study of periodic and non-periodic 

 fluctuations in latitude of the cyclonic and anti-cyclonic belts 

 surrounding the earth is most important in many ways. 



A CONVENIENT modification of the hydrometer method of 

 determining the densities of gases has been devised by M. 

 Meslans, whose apparatus is described and illustrated in the 

 Comptes rendus, No. 11. It consists of two, hollow spheres 

 hung to the arms of a balance. Each sphere, which is made of 

 glass, aluminium, or gilt copper, hangs in a separate compart- 

 ment, the suspending thread being introduced through a hole 

 in the lid. The compartments are enclosed in a box and 

 surrounded by water in order to keep them at equal tempera- 

 tures. They are at first filled with ait- to determine the posi- 

 tion of equilibrium. The gas whose density is to be determined 

 is then introduced through a long tube immersed in the water, 

 and enters one of the compartments, having previously been 

 NO. I 25 I, VOL. 48] 



dried. The gas is passed through in a slow and continuous 

 stream, and if its density differs from that of air, the equilibrium 

 of the balance is disturbed. The weight necessary to re-establish 

 equilibrium is noted, and the density calculated according to a 

 simple formula. Thus the density is found by a single weigh- 

 ing, and by keeping the current of gas continuous any variation 

 in its density is easily observed. A fairly high accuracy is at- 

 tainable, depending upon the sensitiveness of the balance and 

 upon the perfection of gauge of the spheres. One important 

 application of the apparatus is that for determining the density 

 and composition of the products of combustion in furnaces. The 

 scale of the balance is graduated so as to show at a glance the 

 percentage of carbonic acid, and hence the degree of efficiency 

 of the furnace in question. This percentage, which is 21 

 theoretically, never exceeds 18 in practice, except in gas 

 generators. In a great number of works it varies between 6 

 and 8. M. Meslans' apparatus is being applied to the study of 

 the various methods of heating. Another application is that by 

 which the presence and percentage of marsh-gas is indicated. 

 With spheres of I litre capacity and a balance sensitive down to 

 half a milligramme it was found possible to detect 01 per cent. 

 of methane in the air of a mine. 



The Electrical Review, in the course of an article on " I^lec- 

 trical Engineering at the World's Fair," describes the curious 

 rotary effects of a two-phase alternating-current field-magntt. 

 A ring-armature is wound with four coils, connected in pairs 

 across the circle ; one pair is connected to one of the two-phase 

 currents, the other pair to the second current. The ring- 

 armature is then laid horizontally on a table, and a board placed 

 over it. Almost any metallic article placed on the board im- 

 mediately begins to run round above the ring. Copper balls, 

 coins, &c. , or any other easily movable conducting article will 

 at once get into motion. 



The October number of Mind contains an article on theories 

 of light-sensation, by Mr. C. L. Franklin. 



Mr. George Hogben has sent us two papers extracted 

 from the Transactions of the New Zealand Institute, 1892, and 

 referring to earthquakes experienced at the Antipodes in June, 

 July, and December, 1891. 



The lecture on "The Interdependence of Abstract Science 

 and Engineering," delivered by Dr. W. Anderson, F.R.S., at 

 the Institution of Civil Engineers, in May last, has been 

 extracted from the Proceedings of the institution, and is now 

 published separately. 



A course of lectures upon Planetary Astronomy, with espe- 

 cial reference to " The Planet Venus " will be delivered in the 

 theatre of Gresham College, on the evenings of October 24, 25, 

 26 and 27, by the Rev. E, Ledger. 



A HANDY book on " The Art of Projection and Complete 

 i Magic Lantern Manual," by an expert, has been published by 

 \ Mr. E. A. Beckett, Kingsland-road, N.E. Lantern operators 

 \ will find in it many useful hints upon matters of manipulation. 



Messrs. Whittaker and Co. have published the " Prin- 

 ciples of Fitting," for apprentices in engineering and students 

 in technical schools, by a Foreman Pattern Maker. The 

 book is profusely illustrated, and should be of great assistance 

 to the workers for whom it is intended. 



Students preparing for the examination in the "Prin- 

 ciples of Mining " held by the Department of Science and 

 Art, or for colliery managers' examinations, are recommended 

 to use an elementary text-book of " Coal Mining," by Mr. 

 Robert Peel, just published by Messrs. Blackie and Son. The 

 book is very well written and quite trustworthy. 



