no 



NA TURE 



[December 5, 1901 



Season. These experiments have in many cases been going on 

 continuously on the same plots since 1895. so that the results are 

 beginning to show a measure of consistency that is not imme- 

 diately attainable in field trials. Training experiments at Wye 

 are favourable, on the whole, to the systems of wide planting and 

 broad alleys. The umbrella system of training has generally 

 given the maximum weight per acre, but has various disadvan- 

 tages compared with the Butcher system. Cutting the bine at 

 picking time, as is done when hops are grown on poles or on 

 some wire systems, is found to result in a considerable loss of 

 material to the hop plant, and weakening and loss of crop in 

 the succeeding year. Stripping off the lower leaves and laterals 

 is found to be harmful in seasons of short growth and without 

 effect when the plant is vigorous. Cultivation experiments at 

 Goudhurst, where a plot has now carried a full crop for seven 

 years though without any cultivation beyond surface hoeing, 

 aroused considerable discussion ; the trial is to be extended to 

 other soils. Manurial experiments have been carried out on 

 various soils in Kent and Surrey and deal chiefly with the use 

 of mineral manures ; the soil is shown to be the main fiictor in 

 the results attained, especially in the cases where the cultivation 

 has been extended from the typical hoplands to sandy or clay 

 soils. 



The third number of vol. ii. of the Weil Indian Btdlctin, 

 just received from Barbados, contains a good deal of useful 

 information relating mainly to cacao and sugar-canes. Mr. 

 M ixwell-Lefroy, entomologist to the Imperial Agricultural 

 Department, has visited the island of Grenada to investigate the 

 prevalence of an insect pest known as "thrips, " affecting the 

 leaves and pods of the cacao, and apparently to a less extent the 

 leaves of cashew, guava and Liberian coffee. The insect is 

 found also on cacao in the islands of St. Vincent, St. Lucia and 

 Dominica, but is not known in any other part of the world. 

 Thus far its depredations have not been of a very serious 

 character, and to prevent its becoming a greater plague advice 

 is given to the planters as to the methods which should be 

 adopted to suppress it. Mr. Howard, the mycologist, deals 

 with the fungoid diseases of cacao in the West Indies, sum- 

 marising the results obtained by the Department in recent 

 investigations. The subject is fully treated in three divisions — 

 pod diseases, stem diseases and root disease. Mr. William G. 

 Freeman, the technical assistant, in a note on the formation of 

 cane-sugar in the sugar-cane, endeavours to give some idea of 

 the possible sequerice of events, but more investigation is neces- 

 sary to clear up many doubtful points— we require to know, for 

 instance, the first product of assimilation and the true relation- 

 ship to each other of glucose and cane-sugar. Amongst other 

 contributions are Sir W. T. Thiselton-Dyer's note on sugar-cane 

 disease, and Mr. Noel Deerr's article on the distribution of the 

 constituents of the sugar-cane in a Demerara factory and their 

 utilisation as manure. There is an illustrated article on bud 

 variation in the sugar-cane. Information has been collected 

 from the various islands showing the planting and crop seasons 

 of the sugarcane. A full description of Barbados sour-grass, 

 Andropogon perlusus, is given ; and the desirability of intro- 

 ducing insectivorous birds from other countries to prey on ttie 

 insect pests which cause so much destruction in the West Indies 

 is discussed, but the conclusion arrived at seems to be in favour 

 of encouraging the propagation of the local Barbados blackbird 

 and to keep out the East Indian myna or starling, fearing the 

 latter would become a worse pest than the insects. 



A i-REMMiNARY report of the international balloon ascents 

 of June 13 has just been received. The places from which the 

 ascents wore made were Trappes (Paris), Chalais-Meudon, 

 Slrassburg, Berlin, Vienna, Pavlovsk (St. Petersburg), .Moscow 

 and Bath. In six cases the unmanned balloons were lost, or 



the records are not forthcoming. The greatest altitude, 14,800 

 metres, was attained from Trappes, where the lowest temperature, 

 -5i°'4 C, was recorded. The ascent took place about 8h. a.m. 

 temperature at starting, I0°'4, at 6090 m., - 25°, at 10,900 m., 



- 50°. At Strassburg the unmanned balloon ascended at 

 3h. 46 m. p.m., temperature 16°, and went through a thunder- 

 storm cloud ; at 2800 m. the temperature was 0°, at 4500 m. 



-10°, at S400 ni. -15°; the greatest height reached was 

 5700 m., temperature -17°. Another balloon which ascended 

 about the same time reached an altitude of 10,400 m. and the 

 lowest temperature recorded was -49° -9. One of the balloons 

 sent up from Berlin reached a height of 9315 m., temperature 

 ~43°'5. From Vienna an unmanned balloon left the earth at 

 8h. a.m., temperature 22°; at 5000 m. — 20°, and at 8900 m. -63' 

 were recorded. Several manned balloons took part in the ex- 

 periments ; one of two from Vienna, carrying Archduke Leopold 

 Salvator and Captain Hinterstoisser, ascended to 3500 metres, 

 where a temperature of - 4° was recorded. 



Mr. C. V. Drysdale communicated to the Institution of 

 Electrical Engineers last week a description of a new form of 

 permeameter for testing the magnetic qualities of iron and steel 

 in bulk. A special form of hollow drill is used to drill a hole 



- inch deep in the material to be tested ; this hole has its upper 

 part conical, and the small central pin left standing is jV inch 

 in diameter. Into this hole fits a soft iron plug on the lower 

 part of which are wound the magnetising and testing coils. 

 There is thus formed a miniature permeameter in which nearly 

 the whole of the magnetic circuit is of the material under test. 

 By connecting the coils in the plug with suitably graduated 

 instruments the permeability, retentivity and hysteresis may be 

 very easily tested. Curves and figures which were published 

 showed that the instrument gave very consistent results, although, 

 as was pointed out in the discussion, they did not agree as well 

 as they might with the values usually obtained by other permea- 

 meter.s. But the simplicity of the apparatus and the ease with 

 which a test can be obtained (if, that is, the drills can be made to 

 act with uniform accuracy) should give it considerable com- 

 mercial value. The dynamo manufacturer requires chiefly a rough 

 guide to the permeability of the casting he is going to use and 

 does not need very rigid .scientific accuracy, and such a guide 

 Mr. Drysdale's instrument should be able to provide. In fact, 

 any method which really only tests a very small portion of the 

 bulk, whether in silii, as in this case, or after it has been cut off, 

 can never be thoroughly satisfactory. 



Prok. Lebedew, of Moscow University, describes in Drude's 

 Amialen der Physik for November, 1901, a research by means 

 of which he has succeeded in demonstrating experimentally 

 the pressure of light. A translation of his paper is now 

 appearing in the Electrician. It followed as a consequence 

 of Maxwell's theory that the combined effect of the electro- 

 static and electrokinetic stresses is a pressure in the direc- 

 tion of the propagation of the wave numerically equal to 

 the energy in unit volume, and Maxwell pointed out that " the 

 concentrated rays of the electric lamp falling on a thin metallic 

 disc, delicately suspended in a vacuum, might perhaps produce 

 an observable mechanical effect." It was this effect that Sir 

 William Crookes was thought to have obtained in his radiometer, 

 but the magnitude proved many thousand times too great. 

 Prof. Lebedew eliminated the radiometer action by using a large 

 bulb with high exhaus-ticm and by excluding rays capable of 

 heating the tube walls. The radiometer vanes were of very 

 thin aluminium foil suspended by a glass fibre, and the source 

 of light the electric arc. The results obtained agree with the 

 theoretical results of Maxwell within 10 per cent., and show 

 that the pressure is directly proportional to the energy of the 

 incident lipht and independent of the colour. 



NO. 1675, VOL. 65] 



