96 



NATURE 



\yune 4, 1874 



The maximum pressure was found to be equal to sustaining a 

 column of water 3173 ft. high. One of the most interesting 

 portions o( the experiments was to determine, if possible, whether 

 any other force than the vital action of the roots is necessary to 

 produce the sap-pressure. A black birch-tree was selected, and 

 a root was severed at 10 ft. from the trunk, and to it was 

 attached a mercurial gauge. This showed a maximum pressure 

 equal to Sj'Sft. of water, and proved that "the absorbing 

 power of living birch rootlets ^^■ithout the aid of any of the 

 numerous helps imposed upon them by ingenious philosophers, 

 such as exhalation, capillarity, oscillation, &c., was quite suffi- 

 cient to account for the most essential of the curious phenomena 

 connected with the circulation of sap." 



Journal 0/ the FrankHii Institute, April. —The following are 

 some of the important papers in the number : — Repbrt of the 

 Committee of tlie Institute on the Westinghouse car-brake. 

 This brake in its simplest form consists of a small steam-engine 

 placed in the locomoti\e, which, taking steam from the boiler, 

 works an air-pump, which compresses air into a main reservoir, 

 secui'ed beneath the car. By an ingenious arrangement of pipes 

 and automatically acting valves, the air is admitted into a series 

 of brake cylinders, one under each car, the ]Distons of which are 

 connected with and act upon the ordinary brake-levers, and thus 

 apply the brakes to the wlieels. The inventor has made im- 

 portant improvements on this, by means of which the compressed 

 air may be admitted almost mstantaneously into the brake- 

 cylinders, and the train brought to a standstill in an incredibly 

 short space of time ; e.g. a train, going at the speed of thirty 

 miles an hour up a gradient of 29 '6 ft. per mile, was brought to 

 a stop in 16 seconds. .Scott's legacy, premium, and medal, were 

 awarded to the inventor by the Institute.— The principles of 

 shop-manipulation for apprentices is continued. — On tlie 

 mechanical calculation of earthwork (or the results of physical 

 measurements in general) according to the pirismoidal or other 

 formula;, by C. Herschell, C.E. 'This paper relates mainly to 

 the important uses to which the polar planimeter can be put. — 

 Prof R. H. Thurston contributes two papers which have been 

 published separately : On the thermal and mechanical properties 

 of air and other gas, subjected to compression or expansion ; 

 and On the strength, elasticity, and resilience of materials of 

 machine construction ; both papers are illustrated with diagrams. 



The Journal of Mental Science for April, opens with the third 

 number of the Morrisonian Lectures on Insanity for 1873, in which 

 Dr. Skae and Dr. Clouston still further exemplify the classification 

 of the various kinds of insanity according to the bodily disease or 

 condition with which they ore associated. In speaking of 

 Climacteric Insanity it is contended that men between 50 and 

 60 have a critical period corresponding to that passed through 

 by women between 40 and 50 ; but the evidence seems far from 

 conclusive. But nothing can be more striking and terribly in- 

 structive than the amount of insanity of one kind or another that 

 is unmistakably connected with the organs and functions of 

 generation. — The morbid psychology of criminals by David 

 Nicolson, M.B., continues ; and his observations on this unfor- 

 tunate class are very valuable and well worth recording — 

 especially perhaps may they prove usehil " as a basis of com- 

 parison for kindred phenomena occurring in circumstances less 

 definite and uniform." No one is likely to be very seriously 

 injured by the common prison delusion "that their food is 

 poisoned ;" but if the same painful fancy take possession, as it 

 sometimes does, of individuals in the outer world, it may not be 

 so readily recognised as a delusion, and the consequences may 

 be very mournful. — A psychological study of the character of 

 Jean Jacques Rousseau, by J. Hawkes, M.D., suggests the idea 

 of a washerwoman sounding the Atlantic with her clothes line, 

 and finding it very shallow all over. 



Zeitschift dcr Oeslerreichischen GeseUschaft Jiir Meteorologii, 

 April I. — In this number Dr. Mohn furnishes a number of data 

 from three years' observations of the temperature in and near 

 Christiania— at the Institute and the Observatory— and of the 

 decrease of heat with height ; a station iiamed Frognersiiter 

 having been chosen, situated about five miles NN.W. from 

 the Observatory, and 408 metres above the sea. The air within 

 the city is shown (as in other localities) to be warmer than with- 

 out. The temperature in general decreases with the height, and 

 most quickly in May ; in the winter months the decrease is small, 

 and it passes, in December, into an increase. Dr. Mohn studied 

 the meteorological conditions present in three separate cases : — 

 \a) Frognersiiter warmer than Christiania ; (/■) colder and exces- 



sive ; {c) change of temperature on fall of rain or snow. As re- 

 gards («), it occurred in cold weather; the wind N.E. or 

 E., and light; atmospheric pressure about 7mm. above nor- 

 mal ; sky most often clear, but sometimes a mist covered Chris- 

 tiania, while Frogner.sater was in sunshine. The author inquires 

 at some length into the causes of change of temperature with 

 height, and points out that the elements of greatest influence 

 here are the strength of wind and the relative moisture. The 

 change increases with the former and decreases with the latter. 

 To this is joined the action of precipitates, in so far as this, 

 accompanied by greater relative moisture, contributes to lessen- 

 ing the decrease of temperature with the height. — Prof Ebermayer 

 follows with a review (in part) of a new text-book of climatology 

 by Dr. Lorrenz and Dr. Rothe. From personal observation he 

 disputes the authors' assertion that the increase of cells in plants 

 takes place only by night. — Among the "Kleinere Mittheilun- 

 gen," we note some meteorological observations from the north- 

 west coast of Spain. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, May 7. — "Preliminary Experiments on 

 a Magnetised Copper Wire," by Prof Balfour Stewart, LL.D., 

 F.R.S., and Arthur Schuster, Ph.D. 



1. The following experiments were made in the physical labo- 

 ratory of Owens College, Manchester : — 



A copper wire was wound fifty-three times in one direction 

 round tlie poles of a powerful electro-magnet, the length of wire 

 encircling these poles being about twelve metres. 



A Wheatstone bridge was employed to measure the resistance 

 of the wire, and a very delicate Thomson's reflecting galvano- 

 meter, by Elliott Brothers, was likewise used. 



Experiments were made at intervals of two minutes ; and on 

 each occasion the curvent was allowed to pass through the bridge 

 for ten seconds, the measurement being taken by the first swing 

 of the galvanometer, which lasted for about eight seconds. 

 Three cells of Grove's battery were used for producing this 

 current, but on the other hand six similar cells were employed 

 for magnetising the electro-magnet. 



2. In the first experiments made, the induction-current due to 

 the wire coiled round the magnet affected the galvanometer, but 

 after Dec. 12 a solid key put into the circuit was taken out, so 

 that no induction- current passed. 



The following is a specimen of the observations made : — 



Dec. 17, 1873. 

 Whole deflection observed 

 Time of putting on (increasing deflection denotes Condition of 



current. increasing resistance). magnet. 



II II 



'3 

 15 

 17 

 19 



21 



312 

 317 



3" 

 345 

 32« 

 306 

 303 

 293 



off 

 off 

 off 



off 



25 



27 300 oft 



29 290 on 



31 307 off 



li 283 on 



35 292 off 



37 28S on 



39 302 off 



41 292 on 



43 e,°9 off 



It will be seen from this experiment that the first effect of 



putting on the magnetism was a marked increase of resistance ; 



but with this exception the resistance, when the magnetism was 



on, was less than the mean of the two resistances on both sides 



of it, representing the magnetism off. 



3. The arrangement remained untouched, as far as we know, 



from Dec. 15, when it was finally made, until Dec. 19, when 



the experiments were interrupted during the Christmas holidays ; 



and in all cases \\\e first effect of putting on the magnetism was a 



marked increase of resistance. 



It was soon seen that thisyf/'j/ effect had some reference to the 



time elapsing since the last experiments were made. For in- 



