550 



NA TURE 



\_April 7, 1887 



junction were pro-ierly utilisad, a more sensitive instrument 

 would be made than the boloineter, which depends on the 

 chan];e of resistance of a conducting filament with temperature. 

 After showing the defects of the ordinary thermopile, he ex- 

 plained the construction of his instrument. A circuit is made of 

 one turn of I square centimetre, of which three sides are thin 

 copper wire, and the fourtli is a compound bar of antimony and 

 bismuth, each piece being 5 >< 5 '^ u mm., soldered edge to edge. 

 This circuit is supported by a thin rod, to which is fastened a 

 mirror, and the whole is hung by a torsion fibre, so that the 

 circuit is in the field produced by a powerful magnet with 

 suitaljle pole pieces. 



When radiant energy falls on the centre of the bar, the circuit 

 is deflected, and the amount of the deflection measures the 

 energy. The instrument supplies the most delicate means of 

 detecting radiant heat yet made. For instance, the particular 

 instrument made by the author— having proportions which he 

 now know.s to be not the best, and with the Iceeper on the 

 magnet, so that the field was one of lOJ units only^was capable 

 of showing the heat which would be cast on a halfpenny by a 

 candle-flame at a distance of 116S feet, and as the sensibility is 

 proportional to the strength of the field, it would be fully ten 

 times as sensitive with the keeper ofif. 



By calculation it may be shown that an instrument made 

 with certain given proportions, which are easily obtainable, 

 would be capable of showing a change of temperature of the 

 junction of i/iod,ood,ooo of a degree of heat. 



The author also showed a motor consisting of a cross of metal, 

 the centre being antimony and the arms bismuth, to the ends of 

 which are soldered four copper wires, who^e free ends are joined 

 by a ring of copper which rotates rapidly when the spark at the 

 end of a blown-out match is held near it. 



If ithe spark is held on the right-hand side of the north pole, 

 the motor will start itself oscillating through angles which 

 increase until it at last begins to revolve, which it will do 

 indifferently in either direction. If the spark is held on the 

 left-hand side, the motor .at once stops. 



This is interesting in that it is an electro-magnetic motor which 

 goes, having neither sliding nor liquid contacts. 



The author promises, shortly, a complete paper in which the 

 best proportions for the various parts are given, and to show an 

 instrument in which these proportions are employed. 



Geological Society, March 23.— Prof. J. W. Judd, F.R.S., 

 President, in the chair. — The following communications were 

 read : — Notes on the structure and relations of some of the older 

 rocks of Brittany, by Prof. T. G. Bonney, F.R.S. These notes 

 are the results of a visit to some of the more interesting geological 

 sections in Brittany, in the autumn of last year. The author is 

 greatly indebted for information to the Rev. E. Hill, who took 

 part in the summer excursion of the Societe Geologique de 

 France, and to Dr. Charles BarDis, who has for long been 

 engaged in investigating the geology of Brittany, (i) The 

 author briefly noticed the glaucophane-amphibolites and the 

 associated schists of the He de Groi.t, which have been already 

 admirably described by Dr. C. Barrois. (2) The next part of 

 the paper treated of sections in the district about Quimperle. 

 (3) In this part of the paper were noticed the crystalline rocks 

 of Roscoff, and (more briefly) the Palaeozoic strata about 

 Morlaix, with the mineral and structural modifications due to 

 pressure and to the action of intrusive igneous rocks. The 

 author pointed out that, in the latter case, the results either of 

 pressure-metamorphism or of cmtact-metamorphism differ much 

 from the crystalline schists, which, both in Brittany and else- 

 where, are regarded as of Archxan age ; and that here in the 

 north at Roscofl', we have a series of banded gneisses, less 

 modified by subsequent pressure than in the south, the structures 

 of which are very difficult to explain on any theory of a "roll- 

 ing out " of a complicated association of igneous rocks, but 

 which are such as would naturally result from some kind of 

 stratification of the original constituents. The result of the 

 author's work is to strengthen the opinion which he has already 

 expressed, that while the structures of some foliated rocks may 

 be regarded as primarily due to pressure operating on suitable 

 materials, the structure of others seems opposed to this explana- 

 tion. At any rate the latter rocks appear to have assumed a 

 crystalline condition with a semblance of stratification in Pre- 

 Cambrian times ; so that, whatever may be their genesis, they 

 are rightly called Archajan gneisses and schists. — The rocks of 

 5ark, Herm, and Jethou, by Rev. E. Hill. — In opening the 



discussion which took place after the reading of these papers, 

 the President remarked on the value attaching to Prof Barrois's 

 work in Brittany, and on the interest of the observations made 

 on the country by Prof. Bonney. The conclusions as to the 

 Archaean age of the lower gneissose rocks would probably be 

 generally accepted ; but a question which must still be regarded 

 as an open one was, wdiether foliation ever corresponded with 

 original bedding. The supposed instances of unconformity and 

 current-bedding depended on the assumption that such was the 

 case. Mr. Becker, Mr. Rutley, and Dr. Hicks, also took part 

 in the discussion. — Quartzite boulders and grooves in the Roger 

 Mine at Dukinfield, by Mr. James Radcliffe. The statements 

 made in this paper were discussed by Mr. W. W. Smyth, Prof. 

 Boyd Dawkins, Mr. Blanford, and Prof. Bonney. 



Royal Microscopical Society, February 9. — Annual Meet- 

 ing. — Dr. Dallinger was re-elected President for the fourth 

 time. We have already printed the remarks made by Dr. 

 Dallinger in his annual address on the value of the new apo- 

 chromatic lenses. Having dealt with this subject, he proceeded 

 to record the results of experiments as to the changes of tempera- 

 ture to which the lower forms of organisms can be adapted by 

 slow modifications. For nearly seven years continuous experi- 

 ments and observ.ttions were made, with the result that .several 

 organisms had gradually become adapted to live and thrive under 

 a high temperature. Commencing at the normal temperature 

 of 60° F., the first four months were occupied in raising the 

 temperature 10° without altering the life-history. When the 

 temperature of 73° was reached, an adverse influence appears to 

 be exerted on the vitality and productiveness of the organisms. 

 The heat being left constant for tsvo months, they regained their 

 full vigour, and by very gradual stages of increase 78' was 

 reached in five months more. Again a long pause was necessary, 

 and during the period of adaptation a marked development of 

 vacuoles was noticed, which again disappeared when it was 

 possible to raise the temperature farther. The farther history of 

 the experiments presented practically the same feature; — long 

 pauses, vacuolation, slow advance — until at last the high tempera- 

 ture of 158' F. was reached, when the research was accidentally 

 terminated. It is because it is so difficult to observe the effects 

 of changes through a sufficient number of generations of larger 

 animals that results obtained on the simpler forms are so valuable. 

 Darwin distinctly insisted on the slowness of the process of 

 adaptation. The organisms examined by Dr. Dallinger are in- 

 cessantly multiplying by dividing, the longest interval being four 

 minutes : half a million generations must therefore have been 

 observed, giving the " countless generations " required. At the 

 end of the series the organisms were found to be fully adapted to 

 a change in the essential condition of life, sufficient to produce 

 death originally. 



March 9.— Mr. W. T. Suffolk, Vice-President, in the chair.— 

 Mr. E. C. Bousfield exhibited photomicrographs of Amphipkui-a 

 pdluclda, to show what may be expected from the employment of 

 Prof Abbe's new lenses. The objective employed wa-; a very 

 fine 1/8 apochroaaatic homogeneous-immersion i'4 N.A. He 

 also exhibited photomicrographs of salicine crystals as viewed by 

 polarised light, and the colours were purposely selected to test 

 as severely as possible the capacity of the plate used — a Dixon's 

 othochromatic. — Dr. Crookshank exhibited two photomicro- 

 graphs of flagellated Protozoa of the blood. These were taken 

 with Zeiss's 1/18 homogeneous-immersion from a preparation 

 stained with magenta. The amplification (1750) was obtained 

 by enlargement from the original negatives. They illustrated 

 the employment of the Eastman bromide paper, and the value of 

 photomicrographs for teaching purposes. The flagella and the 

 delicate longitudinal membrane were clearly demonstrated. — Mr. 

 W. Watson exhibited and described the Watson-Draper micro- 

 scope, which he had made on the designs of Mr. E. T. Draper. 

 The microscope is an elaboration of the Watson-Crossley form, 

 and the idea of the designer is " that when the object is on the 

 stage, either it may be made to rotate in any direction, horizontal 

 or vertical, round a fixed beam of li^ht without the light ever 

 leaving the object, or the stage maybe kept fixed while the light 

 is revolving round it in any direction, horizontal or vertical, 

 always however remaining upon the object." — Mr. J. Mayall, 

 Jun., described the Nelson model microscope exhibited by 

 Mr. C. Baker. — Two papers were read : by Mr. G. Massee, on 

 the differentiation of tissues in fungi ; and by Drs. H. J. 

 Johnston-Lavis and G. C. J. Vosmaer, on cutting sections of 

 sponges and other similar structures with soft and hard tissues, 



