530 



NATURE 



[February i6, 191 i 



in^ 



be of value on account of the relatively long duration of 

 its effect. Methyl-stovaine is the least readily decomposed 

 by faintly alkaline fluids such as lymph and cerebro-spinal 

 fluid. Fourneau's new salt has the least effect on circula- 

 tion and on respiration. — F. F. Blackman and A. M. 

 Smith : Experimental researches on vegetable assimilation 

 and respiration. VIII. — .A new method for estimating 

 gaseous exchanges of submerged plants. The plant is 

 enclosed in a glass chamber, a current of water is kept 

 flowing through the chamber, and samples of the affluent 

 and effluent liquid are analysed at frequent intervals. The 

 alteration in the amount of CO^ in solution which the 

 liquid undergoes in passing over the plant in the chamber 

 is the measure of the respiration or assimilation that is 

 taking place. For experiments on assimilation, the liquid 

 supplied to the chamber can be enriched with any desired 

 amount of CO^, and by a special use of a CO^ generating 

 tower the amount of this gas dissolved can be kept con- 

 stant for a long period of time. The glass chamber con- 

 taining the plant is sunk in a large copper water-bath 

 with a glass window, and the temperature and illumina- 

 tion can be controlled. When the conditions allow 

 vigorous assimilation, much oxygen is given off as bubbles 

 from the plant in the chamber, and these bubbles take up 

 an appreciable amount of CO^ from the solution. It is 

 therefore necessary to collect and measure this gas and 

 use it as a correction to the apparent diminution in the 

 dissolved CO,. The gas is separated from the liquid by 

 a valve at the highest point of the apparatus, and collected 

 automatically for analysis. This method has none of the 

 limitations of the bubble-counting procedure exclusively 

 employed previously for the investigation of the assimila- 

 tion of water-plants, and, since it takes account of the 

 CO, in solution and also of that in the gas bubbles, critical 

 measurements can now be made of the assimilation 

 throughout the whole range of the external factors that 

 primarily control this function. — F. F. Blackman and 

 A. yi. Smith : Experimental researches on vegetable 

 assimilation and respiration. IX. — On assimilation in sub- 

 merged water-plants and its relation to the concentration 

 of carbon dioxide and other factors. The experiments 

 were carried out by a new method, which takes account 

 of the alteration of the gases in solution as well as of the 

 gases liberated as bubbles. The aim is to demonstrate the 

 nature of the relation between assimilation and the chief 

 environmental factors — CO^ supply, light-intensity, and 

 temperature. The relation is such that the magnitude of 

 this function in every combination of these factors is deter- 

 mined by one or other of them acting as a limiting factor. 

 The identification of the particular limiting factor in any 

 definite case is carried out by apph'ing experimentally the 

 following general principle : — When the magnitude of a 

 function is limited by one of a set of possible factors, 

 increase of that factor, and of that one alone, will be 

 found to bring about an increase of the magnitude of the 

 function. From the data obtained, a new type of diagram 

 is constructed, by which it is possible to foretell what value 

 of assimilation in Elodea will be attained in any combina- 

 tion of medium magnitudes of the three factors of the 

 environment. In this diagram, against the different values 

 of assimilation as ordinates, are ranged three separate 

 curves showing the degrees of CO, supply, temperature, 

 and illumination, which are respectively essential for the 

 attainment of each value of assimilation. For any hyf>o- 

 thetical combination of the factors, it follows, by the prin- 

 ciple of limiting factors, that if the three functional values 

 corresponding potentially to these be ascertained from the 

 diagram, then the actual magnitude of assimilation 

 attained with that combination of factors will alwaj's be 

 the smallest of the three potential values. The last section 

 contains a critical account of the work of previous investi- 

 gators who interpreted their results on the assumption that 

 there was a primary optimum in the relation between 

 assimilation and each external factor. The substantial 

 work of Pantanelli led him to the conclusion that the 

 position of the optimum for any one factor shifts with the 

 magnitude of the other concurrent factors. This can only 

 be a transitional point of view, and from this we have 

 advanced to the standpoint that the whole conception of 

 optima in this connection is inapplicable, and breaks down 

 completely on careful analysis. The authors show in detail 

 that all the experiments of previous workers are more 



NO. 2155, VOL. 85I 



harmoniously interpreted from the point of view of in 

 acting limiting factors than by the conception of optima! 



Geological Society, January 25.— Prof. W. W. Wal 

 F.R.S., president, in the chair. r—H. H. Thomas : The 

 Skomer volcanic series t^'embrokeshire). The rocks are 

 traceable on the mainland from near St. Ishmaels on Mil- 

 ford Haven to VVooltack Head, and on the west occupy 

 the islands of Midland, Skomer, and the Smalls. ! 

 thickness exposed is some 3000 feet, and the lal' 

 extension some twenty-five miles. The chief evidence 

 indicates that the rocks are of pre-Upper Llandovery age, 

 but, from a consideratfcn of the geology of the neighbour, 

 ing country, it is probable that their true age is .\n i 

 The rocks are chiefly subaerial lava-flows, frequently in 

 stratified with red clays They are separated into 

 main groups by a mass of sedimentary rocks barren 

 fossils. The lavas form well-defined groups. The r(. 

 fall into eight chief types, two of which are of neces 

 new; in order of increasing basicity they are: — si 

 rhyolites, soda-trachytes, keratophyres, skomerites, mar 

 sites, mugearites, olivine-basalts, and olivine-doler; 

 The first five types may be included in the alkaline ch 

 they are rich in soda, and most of the felspars belon- 

 albite-oligoclase varieties. The last three types are normal 

 subalkaline rocks, in which the felspars range from oligo- 

 clase to labradorite. 



February 8.— Prof. W. W. Watts, F.R.S., president, in 

 the chair. — Prof. T. W. Edgeworth David gave an account 

 of the researches pursued by him, in conjunction 

 with Mr. R. E. Priestley, geologist to the British Antarctic 

 Expedition of 1907-9, in the course of that expedition, 

 more especially the investigations connected with glacial 

 geology. 



Physical Society, January 27. — Prof. C. H. Lees, F.R.S., 

 vice-president, in the chair. — Prof. F. T. Trouton : A 



demonstration of the phase difference between the primary 

 and secondary currents of a transformer by means of a 

 simple apparatus. The apparatus is a primitive induction 

 motor consisting of two horseshoe electromagnets with 

 their axes coincident and vertical, and their planes at r'n' 

 angles. Above the poles a copper disc is pivoted. J 

 primary current from a transformer is sent through • 

 magnet and the secondary current through the ou 

 With a suitable phase difference a rotating magnetic ! 

 is thus obtained. Inserting an iron core into the tr. 

 former diminishes the speed of rotation. A steel core 

 produce a greater negative rotation than an iron one. 1 

 demonstrate the hysteresis effect, it is necessary that the | 

 core should consist of a bundle of fine wires, otherv''"^" 

 the Foucault currents set up will introduce a lag. 

 effect of Foucault currents can be shown by introduc , 

 another coil within the transformer in place of the iron j 

 core and closing its circuit with a variable resistance. — ' 

 Prof. J. A. Fleming: : A note on the experimental measn 

 ment of the high-frequency resistance of wires. 1 

 author refers to a paper read by him in December, u;<^-., 

 before the Institution of Electrical Engineers, on quanti- ! 

 tative measurements in connection with radio-telegraphy • 

 (Journal Inst. Elec. Eng., vol. xliv., p. 349, 1910). in j 

 which he described an apparatus consisting of a differ- 1 

 ential air thermometer having tubular bulbs into which j 

 similar wires could be placed, and by means of which 

 a comparison could be made of the high-frequency (H.F.); 

 resistance R' of a straight wire and its steady or ohmic ! 

 resistance R. If two equal wires have passed through j 

 one a steady current A, and through the other a _H.F. 

 current -A,, then if these currents are adjusted until the 

 rate of heat evolution in each case is the same, we have, 

 A°R = A|-R'. Certain precautions are described in thej 

 paper for eliminating inequalities, but by means of correct 

 reading H.F. ammeters as devised by the author, the ratio; 

 of the resistances R'/R can be determined from the ratio | 

 of the mean square currents A^/A,-. — Prof. J. A. Fleminar, 

 and G. B. Dyke : The measurements of energy losses in 

 condensers traversed by high-frequency electric oscillations. , 

 In this paper an arrangement of apparatus is described ; 

 for the purpose of measuring the internal energy losses 

 in condensers traversed by high-frequency (H.F.) current^ j 

 It is shown that these energy losses in condensers mav be' 

 considered as if they were due to a resistance loss *" *| 

 hypothetical resistance in series with the condenser, the 



