December 22, 1910] 



NATURE 



249 



fixed. When the filament (which in the latest form is of 

 tungsten) is glowing, a current will flow if an E.M.F. is 

 applied between the negative terminal of the filament and 

 the metal plate ; the current can flow from the filament to 

 the plate, but not in the reverse direction, and thus rectifi- 

 cation results. Owing to the upward trend of the con- 

 ductivity curve a much higher sensibility is obtained by 

 applying a certain constant E.M.F. on which that due to 

 the oscillations is superimposed. Passing to the question 

 of the spark, the lecturer reproduced some interesting 

 records showing how greatly the secondary current is in- 

 creased when the spark gap is subjected to an air blast. 

 Finally, Prof. Fleming showed his new form of spark dis- 

 charger. This is of the Wien " quenched-spark " type, 

 and consists of two heavy steel circular discs, one above 

 the other, very perfectly surfaced and with an air gap of 

 \ mm. between them. The lower disc is stationary and 

 the upper one is rotated. The discs are placed in oil, and 

 as there is a hole in the lower disc there is a continual 

 circulation of oil. The discharger is found to give very 

 satisfactory and uniform results, and has been used for 

 measuring losses in condensers. 



Mr. R. W. Paul gave several demonstrations of kine- 

 matograph diagrams. One series, due to Prof. R. W. 

 Wood, illustrated sound waves ; but certainly the most 

 effective films were those due to Prof. S. P. Thompson, 

 F.R.S., showing the movement of fines of force as a 

 keeper approaches a magnet, the starting of a current in 

 a solenoid, the rotation of a dynamo armature (in section), 

 and other similar phenomena. These must have appealed 

 strongly to teachers of magnetism. 



As regards the apparatus exhibited, it may be said that 

 there were many interesting new instruments, though 

 perhaps nothing very striking, and there was much excel- 

 lence in many exhibits that were not essentially novel. 

 Thus in optical work A. Hilger, Ltd., gave an excellent 

 display of spectroscopic instruments and a beautiful 

 demonstration of anomalous dispersion. R. and J. Beck 

 showed a small spectroscope giving large dispersion and 

 with a sine motion so as to give wave-lengths direct. 

 Carl Zeiss, as usual, gave an interesting exhibit, including 

 the movement of gold particles (stated to be about 6 y-ft. 

 in size) in colloidal solution, a special " cardioid " con- 

 denser being used, consisting of two lenses combined, and 

 so shaped that a top illumination is secured for a dark 

 ground, although the beam of light comes from below the 

 centre of the stage. Messrs. E. Leitz showed a large 

 projection apparatus giving excellent definition. 



Photometric apparatus was not so much in evidence as 

 on former occasions, but R. and J. Beck, and also Everett, 

 Edgcumbe and Co., showed very small portable photo- 

 meters for measuring surface brightness and illumination. 

 As an exhibit of general interest may be mentioned that 

 of Strange and Graham illustrating flapping flight. Two 

 wings are worked by " \'ilcar " mechanism, and a dis- 

 tinct upward pull is noticeable, apparently due to the 

 upward path of the wing differing from that on the down- 

 ward stroke. 



The largest number of exhibits, as usual, were electrical. 

 Several interesting thermo-electric exhibits were shown by 

 the Cambridge Scientific Instrument Co., among which 

 may be mentioned an arrangement for keeping the cold 

 junction of a clinical recording thermometer at a constant 

 temperature. This junction is covered by a small Dewar 

 vacuum vessel, and is surrounded by a heating coil, which 

 comes into action as soon as the temperature falls below 

 a certain value ; by this means the temperature of this 

 junction is maintained constant to o-i° C. This firm also 

 showed compensating leads consisting of copper and copf)er- 

 nickel alloy ; these are run in series with the pyrometer, 

 and, being thermo-electrically equal to the platinum/ 

 platinum-iridium couple, they transfer the cold junction of 

 the pyrometer to the galvanometer, thus securing less 

 variation in temperature of the cold junction. An arrange- 

 ment whereby a constant E.M.F. is obtained for applying 

 to a pyrometer so as to secure a false zero was also shown, 

 and we noticed a convenient piece of apparatus for tracing 

 recalescence curves ; also an improved form of C. T. R. 

 Wilson's tilting gold-leaf electroscope. A new form of 

 radiation pyrometer which does not require focussing was 

 shown by the Foster Instrument Co., who also exhibited 

 some special thermo-junction alloys. H. Tinsley and Co. 



NO. 2147, VOL. 85] 



showed a set of instruments largely due to Dr. C. V. 



Drysdale, and some interesting vector diagrams of 

 alternating magnetic flux in an iron wire, obtained by 

 Drysdale 's alternate-current potentiometer. This firm also 

 showed a simple and strong form of vibration galvano- 

 meter based on the familiar Kelvin galvanometer ; a heavy 

 permanent magnet is provided for the control, and the 

 tuning is effected (without affecting the zero) by magnetic- 

 ally shunting this magnet to the desired extent. The 

 alternating current traverses a small coil, which can be 

 easily changed, and the makers state that the instnmient 

 can be used for alternating pressures down to i/iooth 

 micro-volt. R. W. Paul exhibited a well-designed new 

 type of decade standard resistance box with switch con- 

 tacts, the case being filled with oil, and we noticed some 

 new transforming apparatus by Leslie Miller and by Muir- 

 head and Co. Since there were thirty-five exhibitors, we 

 need scarcely say that there was a good deal to be seen, 

 but in the above notes we have only been able to refer 

 very briefly to a few of the more interesting items. 



INVESTIGATIONS ON WHEAT IN INDIA.^ 

 'T'HE importance of the wheat crop in India is not 

 -*■ always realised at home. Until the last few years 

 we received more wheat from India than from Canada 

 or Australia^sometimes more than from both countries 

 put together. At the present time wheat represents some 

 7 per cent, of the total value of merchandise exported 

 from India, but the amount exported is only about one- 

 tenth of the total production, the remaining nine-tenths 

 being consumed in the country itself. \\'hen an industry 

 has reached such great dimensions without excessive nursing 

 it is clear that those engaged in it have consciously or 

 unconsciously adopted tolerably satisfactory methods of 

 working, and any attempt on the part of an outsider to 

 effect improvements must be developed cautiously. When 

 in 1906 the Indian Board of Agriculture decided to take 

 up the matter seriously, they entrusted the work to Mr. 

 and Mrs. Howard, and subsequent events have amply 

 ji stifled the wisdom of their choice. Several important 

 papers have been issued, and finally a volume, *' Wheat 

 in India," in which the authors summarise the present 

 position of the problem and indicate the lines on which 

 advancement may be hoped for. 



Mr. and Mrs. Howard devote the first half-dozen 

 chapters of their volume to a general sketch of wheat- 

 growing in India. Wheat is fairly widely distributed over 

 the country, but the areas where it is really important all 

 lie to the north or on the Central Plateau above the Ghats. 

 In the north-west a great deal of the wheat is irrigated ; 

 the Punjab is especially well suited to canal irrigation by 

 reason of its never-failing snow-fed rivers and its level 

 tracts of land, but recourse is also had to irrigation by 

 wells. On the other hand, in the Central Provinces, 

 Bengal, and Bombay, only a small area is artificially 

 watered. 



In general, the soil is thoroughly well ploughed or 

 scarified during the monsoon and previous to sowing, as 

 many as fourteen ploughings being sometimes given. A 

 good deal of manure is applied in the northern districts, 

 but usually to the maize crop preceding the wheat ; in 

 the Central Provinces the monsoon (kharif) crop of rice, 

 which precedes wheat, is slightly manured, but in Bombay 

 the irrigated wheat itself is manured. Harvest begins in 

 the Central Provinces in March, elsewhere in April, May, 

 and even the end of June in the frontier districts. The 

 wheat for export has to be got to Karachi for shipment 

 as soon as possible, or it rapidly deteriorates, and is 

 attacked by moths and weevils. In the rush the railway 

 resources are heavily taxed, just as they are in Canada ; 

 the Indian case is, indeed, the worse, as there is no 

 elevator system. 



These preliminary chapters are illustrated by maps, 



1 " The Milling and Baking Oualiiies of Indian Whfat." No. 2. By 

 Albert Howard and Gabrielle L, C. Howard. 



"The Influence of Environment on the Milling 'and "Bakirg Qualities of 

 Wheat in India.' By Albert Howard. H. M. Leake and Gabrielle L. C. 

 Howard. (Pusa : Agricultural Research Institute.) 



"Wheat in India, its Production, Varieties and Improvements." By 

 .\lbert Howard^and Gabrielle L. C. Howard. Pp. ix+238. (Calcutta: 

 Thacker, Spink and Co. London : W. Thacker and Co., n.d.) 



