traces of careful chipping or flaking. The implements de- 

 scribed and figured by Mr. Lovett do not belong to a highly- 

 finished type ; indeed, from the enormous number of flakes 

 and chippings associated with them, it is highly probable that 

 the cave was a neolithic workshop. The opinion is expressed 

 that, at the time when the cave was inhabited, Jersey was 

 probably joined to France, and perhaps France to England, 

 which may explain the presence of chert from Portland. 



The current number of L Astronoime contains an article by 

 ]VL J. R. Plumandon on the application of meteorology to the 

 art of war. The author quotes a number of passages from 

 works of military history, showing how a foreknowledge of the 

 weather for a day or so in advance would probably have changed 

 the issue of certain engagements. With the view of facilitating 

 weather predictions, and of utilising them for military purposes, 

 the author has invented a meteoroscope, which is made by M. 

 Richard, of Paris ; it is an aneroid having a dial giving i6o 

 simple predictions according to the reading of the barometer, 

 the wind direction (as shown by the clouds), and the season. It 

 is apparently similar in principle to a synoptic table pubUshed 

 by the author some years ago, in which an index, when made to 

 point to the wind direction, gave at right angles the direction of 

 -the centre of low pressure (Buys Ballot's law), then in con- 

 centric circles was given the probable weather for certain baro- 

 metric conditions and for the particular season, based upon 

 average conditions obtained from a large number of actual cases. 

 The plan is founded upon scientific principles, but the apparatus 

 can only be regarded as a popular indicator of possible changes 

 in accordance with certain general types of weather. 



Mr. J. J. Hicks has sent us an account and some readings of 

 Bartrum's open-scale barometer. The lower part of the instru- 

 ment is like an ordinary mercurial barometer, and near the upper 

 surface of the mercury the tube is enlarged, while above the 

 surface it is again reduced and continued upwards for a length 

 of 27 inches or more. The narrow tube above the mercury 

 contains a red fluid, the upper end of which gives tbe barometer 

 reading ; a rise of mercury in the enlarged part of the 

 tube causing a much greater rise of the fluid in the upper tube. 

 The arrangement is very ingenious, and the readings agree well 

 with the mercurial barometer reduced to a temperature of 62°, 

 after the application of certain corrections, but we do not see 

 why the correction should not be altered to agree with the stan- 

 dard temperature of 32° instead of 62°. By the adoption of 

 artificial inches, and adjustment at some neutral point, the 

 error for capacity might possibly be eliminated. An inch of 

 mercury is represented on the scale by about 9 inches, and it is 

 claimed that this long range enables a reading to be taken to 

 one-thousandth of a mercurial inch without a vernier. The 

 instrument appears to be more reasonable and accurate than 

 other large scale barometers hitherto introduced, and is certainly 

 more handy. 



The best method of using oil in calming troubled waters is 

 thoroughly investigated in a pamphlet entitled " Die Lehre von 

 der Wellenberuhigung," written by Dr. M. M. Richter. The 

 author calls attention to a fact of paramount importance, viz. 

 that the quieting effect of all oils or soaps used is in direct pro- 

 portion to the amount of free oleic acid they contain. The chief 

 desiderata in an efficient material for the purpose are chemical 

 and physical stability, safety, and speed of expansion over the 

 surface of the water. Such a substance would be found in free 

 oleic acid dissolved in methyl or hexyl alcohol. The advantage 

 of the alcohol is twofold. It prevents the solidification of the 

 oleic acid at 4°C., and it greatly increases the rate of expan- 

 sion. The latter depends, as the author shows, not so much 

 .upon a difference of surface tension as upon the solubility of the 

 expanding surface in water. The observed fact that the more 

 NO. 1273, VOL. 49] 



viscous oils are more effective than the more mobile ones, is 

 accounted for by the process of manufacture. Olive oil is pre- 

 pared by pressing out the olives in the cold, while the various 

 fish oils are prepared at high temperatures, and are much more 

 efficient, owing to the decomposition of the oleic glyceride into 

 glycerine and free oleic acid. Bat to save the prejudices of 

 experienced navigators, who have found the more viscous oils 

 answer their purpose better. Dr. Richter recommends that the 

 oleic acid mixture be kept as viscous as possible. The force 

 with which a drop of oleic acid spreads over the surface of sea 

 water is sufficient to arrest the motion of a log of wood weigh- 

 ing as much as fifteen grams, when blown by a fairly strong 

 wind, and even to start it in the opposite direction. 



At a recent meeting of the Societe Francaise de Physique, 

 M. Pellat read a paper on the point of application of electro- 

 magnetic forces. In the classic experiment of Foucault, where 

 a disc of copper turns between the poles of a magnet, the electro- 

 magnetic forces acting on the induced currents, which are 

 developed in the moving disc, do not perform any work, as can 

 be seen from the following consideration. If we rotate the disc 

 by expending an amount of work W, say by means of a falling 

 weight, when the driving force ceases to act, the disc will be 

 rapidly brought to rest. If now the disc is brought back to its 

 initial state by the removal of the quantity of heat Q which has 

 been developed, then T=:JQ where T is the total work done by 

 external forces on the system (disc). Now T is made up of two 

 parts : (i) the work W supplied by the falling weight, (2) the 

 work (r) performed by the electromagnetic forces (also external 

 forces, since we are not considering the magnet as forming part of 

 the system under consideration). Therefore W -f x = EQ ; but 

 Viollehas shown that W = JQ, hence x = o, or the work done 

 by the electromagnetic forces is zero. If, as is usually done, 

 we suppose that the electromagnetic forces act on the matter 

 conveying the electric currents (in this case the disc), then the 

 resultant of these forces is so directed that if the point of appli- 

 cation were displaced during the rotation they would perform 

 a negative amount of work. Hence since x — o the point of 

 application of the electromagnetic forces does not move as the 

 disc rotate-. If, however, we suppose that the electric current 

 is the pomt of application of the electromagnetic forces, then, 

 as has been shown by Nobili, Antinori, and Matteucci, the 

 position of the induced currents being fixed with reference to 

 the magnet, there will be no work done by these electromagnetic 

 forces. To explain how the energy of rotation of the disc 

 becomes converted into heat, it is sufficient to admit that the 

 induced currents (whose positions are fixed in space) exert a kind 

 of friction on the moving disc. The following mechanical de- 

 vice is mentioned by the author as giving a representation of 

 what happens in the electrical case : a copper disc D has its 

 opposite faces pressed between the two arms of a clip P in such 

 a manner that if the clip is held the disc turns with some friction. 

 If the disc and clip are set in movement by the expenditure of 

 an amount of external work W, then, if nothing prevents it, the 

 clip will be dragged round by the disc. If, however, a pin B is 

 placed so that the clip cannot rotate, then the disc will lose its 

 energy of rotation, which will be converted into heat ,by the fric- 

 tion of the clip. The external force which has acted, i.e. the 

 pressure exerted by B on the clip, has performed no work since 

 its point of application has not moved. The quantity of heat 

 developed in the disc and clip will be the equivalent of the 

 work W spent in putting the disc in rotation. Thus the clip 

 represents the induced currents in Foucault's experiment, and 

 the pressure exerted by the pin B on the clip represents the 

 electromagnetic force. 



A COPY of the " Handbook of Jamaica," published by Mr. 

 Edward Stanford, has been received. The work is now in its 

 fourteenth year of publication, and comprises statistical, his- 



