94 



NA TURE 



[July 15, 1922 



with chiefly at Cambridge ; while Aberystwyth, the 

 Welsh plant-breeding station, is concerned principally 

 with the discovery of the production of new and 

 improved herbage plants which must be so important 

 in the West of England from the point of view of 

 pasture and meadow s. 



(c) Plant Physiology. — The chapter on this subject 

 opens with a suggestive discussion on the fundamental 

 principles involved in crop production. These prin- 

 ciples are concerned with the causes that determine 

 heavy cropping and light cropping, resistance to 

 disease, and the formation of flower-buds on fruit- 

 trees. The electrical treatment of crops is also 

 receiving attention at Rothamsted, the Harper 

 Adams Agricultural College, and on a station near 

 Dumfries. To quote from the report, " There is no 

 doubt that electrical discharge will increase plant 

 growth, and it is hoped that it will be found possible 

 to continue the patient experimental work that has 

 been going on for some years, for it seems certain 

 sooner or later that electricity must play an important 

 part on the farm in increasing crop production." 



(d) Fruit-growing and Preserving. — Fruit problems 

 are being dealt with mainly at the horticultural 

 station at Long Ashton and at East Mailing in Kent. 

 Much suggestive work has been done on the problem 

 of fruit stocks, a subject that has hitherto been 

 very confused and unsatisfactory. The Paradise 

 stock, for instance, has been proved to be a mixture of 

 several varieties, and it would appear that even the 

 crab stock may be graded into several classes, each 

 of which has a distinct influence on the scion that is 

 grafted or budded on to it. This subject is in- 

 separably connected with the development of the 

 root system, a line of research to which the la*e 



Mr. Pickering gave much attention, showing that 

 it was quite unnecessary to give the amount of 

 attention that is usually bestowed upon planting. 

 This unexpected result appears to have been con- 

 firmed at Long Ashton, the original root system 

 playing practically no further part in the growth of 

 the transplanted tree, which seems to develop a 

 new root svstem independent of the old. Work on 

 ringing, pruning, disbudding, etc., also promises to 

 have an influence on commercial production, while 

 much light is being thrown upon the problem of 

 manuring of fruit. This station has also contributed 

 largely to our knowledge of the factors that determine 

 the production of high-grade cider and perry. 



(,) I'luul Diseases. — In no department of the 

 Ministry's scheme has more activity been shown 

 than in the direction of plant diseases. At the 

 School of Botany in Cambridge special attention has 

 been given to the silver leaf disease, a trouble that 

 is increasing markedly in this country, and is now 

 no longer confined to plums, but has spread to 

 apples and other fruit-trees. How destructive the 

 disease may be is proved by the fact that an apple- 

 orchard of about 6 acres, near Wisbech, showed 

 more than iooo trees attacked by this disease, the 

 cause being attributed to carelessness in pruning 

 and the neglect to protect the wounds thus caused. 



Space does not permit of the publication of details 

 in the departments of animal husbandry, animal 

 breeding, dairying, animal diseases, and agricultural 

 economics, but enough has probably been said to 

 show what an enormous change has come over th^ 

 country in respect of the provision for agricultural 

 resean h under the enlightened policy pursued by the 

 M r.-=try of Agriculture. 



The Magnetic Work of the Carnegie Institution. 1 

 By Dr. C. Chree, F.R.S. 



I 



"■HE primary object of the volume referred to 

 below is to chronicle the results of observations 

 made on land by members of the Department of 

 Terrestrial Magnetism of the Carnegie Institution. 

 Washington, from 1914 to 1920. During that period 

 1747 stations were occupied, bringing up to 4028 the 

 number of land stations occupied since the world survey 

 began in 1905. Even the general reader will find much 

 to interest him in the field observers' reports on pp. 

 98-222. Mr. F. Brown, for instance, who travelled 

 <>\ er large areas in China, Mongolia. .Manchuria, Lfpper 

 Burma, the Cameroons, and French Equatorial Africa, 

 and who crossed Central Africa from Angola to 

 Mozambique, relates adventures with brigands, lions, 

 witch doctors, and native kings. 



There is also a general account of the land instru- 

 ments emploved, references being made to earlier 

 volumes for "constructional details. Plate 2 gives 

 illustrations of the instruments supplied l>\ the 

 Department to Captain Roald Amundsen's \daud 

 expedition. On p. 9 there is an explanation of the 

 two standards which have been used, the earlier 

 denoted by C.I. W. (Carnegie Institution, Washington), 

 the later by I. M.S. (International magnetic standards). 

 I In use of the latter term for standards which have 

 not received international sanction is somewhat open 

 to criticism. 



The observational results occupy some 67 pages, 

 and later in the volume there is a detailed description 

 of the stations. Some of the more picturesque places 

 visited are illustrated in seven plates. 



1 Researches of the Department of Terrestrial Magnetism, vol. iv. : Land 

 Magnetic Observations 1OT4.-1920. By Dr. L. A. Bauer and 1 thei and 

 Special Reports. (Publication 175). Pp. vi +475+9 plates. (Washington: 

 Carnegie Institution, 1921.) 



NO. 275O, VOL. I IO] 



Mr. ]. A. Fleming describes the construction at the 

 headquarters of the department, at Washington, of 

 a new non-magnetic building for experimental work. 

 It is of considerable size, 28 ft. x 53 ft. ground area, 

 of double-walled concrete. Provision is made for the 

 supply of water, gas, compressed air, and electric 

 circuits for direct and alternating current. The cost, 

 cm lusive of the internal equipment, was 8500 dollars. 

 A magnetic survey made alter the completion of the 

 building showed differences of 2' in dip and 257 in 

 horizontal force between the north and south ends. 



Mr. H. W. Fisk discusses errors arising from minute 

 pivot defects in dip needles. He advocates the use of at 

 least four needles at each station, so as to recognise with 

 certainty when an individual needle becomes faulty. 



A description by Mr. S. J. Barnett of a new sine 

 galvanometer for determining H (horizontal force) is 

 of special interest at the present moment. The con- 

 struction of similar instruments has been simultane- 

 ously in progress in America, Japan, and England. 

 The instrument described by Mr. Barnett is much 

 smaller than that recently described to the Royal 

 Society by Mr. F. E. Smith. Its coils, of approxi- 

 mately 30 cms. diameter, are wound on Carrara, 

 marble. An approximation is made to the Helmholtz 

 arrangement, but the coils are really spirals. It is 

 hoped to measure H with an error less than 1 in 10,000. 

 A preliminary comparison with the I. M.S. standard 

 mentioned above gave a discrepancy of only 0-77, or 

 1 part in 25,000, but the constants of the instrument 

 are as yet to some extent provisional. 



Mr. ]. A. Fleming also deals with the results of 

 comparisons, direct and indirect, between Carnegie 

 Institution instruments and the standard instruments 



