July 8, 1920] 



NATURE 



577 



1)\ the Admiralty and by the Ministry of Agri- 

 ( ulture and Fisheries, and is the standard form of 

 current meter now used by both Departments. 



In the new chap. xx. the " Doug-las-Schafer " 

 -bounding- traveller is described on pp. 434-36, but 

 as this is the official method of obtaining- sound- 

 ings in H.M. surveying- vessels, it would have 

 been more suitably placed at the commencement 

 of this chapter than among- the miscel- 

 laneous collection of methods which are largely 

 experimental. 



Several new methods connected with sweeping 

 are now described in the new material of the book, 

 and all have something to be said in their favour; 

 but it is much to be hoped that the results of 

 mine-sweeping, which developed into such a 

 gigantic and well-organised piece of war 

 machinery, will eventually assist in the devising 

 of some form of thoroughly effective sweep for 

 surveying purposes. 



This last remark applies similarly to the im- 

 provement of surveying devices and methods 

 generally. During the war such enormous pro- 

 gress was made in so many directions affecting 

 scientific developments that many surveying 

 methods must of necessity be entirely, or at least 

 very drastically, altered to bring them up to date. 

 The remarks under the heading " Recent Develop- 

 ments " on p. 470. which deal with this aspect, 

 are, however, distinctly on the conservative 

 side, as it is considered that the scrapping of 

 old systems must be adopted in a very wholesale 

 manner rather than that attempts should be made 

 at their modification to conform to the most 

 modern methods. It is perhaps somewhat difficult 

 to appreciate what an enormous saving of time, 

 and, therefore, of expense and labour, will even- 

 tually result from the introduction of many of 

 these methods into hydrographical surveying, but 

 a good example will be found in connection with 

 the use of hydrophones, by the aid of which accu- 

 rate positions afloat can be obtained in as many 

 hours instead of days or even weeks, which would 

 have formerly been required under the procedure 

 described under the heading " Triangulation by 

 means of Floating Moored Beacons " in the new 

 chap. xxi. 



The war, in fact, has shown the necessity in 

 this, as in so many other directions, of revising 

 the text-books which deal with technical subjects, 

 and this is the condition of affairs as regards 

 hydrographical surveying. The work under 

 notice is undoubtedly the standard publication on 

 the subject, and has a well-deserved and world- 

 wide reputation ; but it is considered that all such 

 standard works on technical matters, such as that 

 now under discussion, should be prepared and 

 NO. 2645, VOL. 105] 



published by the Government Department which 

 is directly concerned, and, therefore, in a position 

 to obtain the fullest information in every possible 

 direction ; and lastly, but not least in impprtance, 

 w^hich is also in a position to keep such an official 

 work always up to date by the periodical publica- 

 tion of supplements. 



Forestry, Tree Diseases, and Timber, 



(i) Our National Forests: A Short Popular 

 Account of the Work of the United States 

 Forest Service on the National Forests. By 

 Dr. Richard H. Douai Boerker. Pp. lxix + 238. 

 (New York : The Macmillan Co. ; London : 

 Macmillan and Co., Ltd., 1918.) Price 12s. 6d.. 

 net. 



(2) Commercial Forestry in Britain: Its Decline 

 and Revival. By E. P. Stebbing, Pp. vi-f 186. 

 (London : John Murray, 1919.) Price 65. net. 



(3) National Afforestation. By A. D. Webster. 

 Pp. 160, (London : T. Fisher Unwin, Ltd,, 

 19 19.) Price 65. net. 



(4) Manual of Tree Diseases. By Dr. W. Howard 

 Rankin. (The Rural Manuals.) Pp. xx4-398. 

 (New York : The Macmillan Co. ; London : 

 Macrpillan and Co., Ltd., 1918.) Price 125. 6d. 

 net. 



(5)-(8) A Map of the World (on Mercator's 

 Projection), Having Special Reference to Forest 

 Regions and the Geographical Distribution of 

 Timber Trees: Timber Map, No. i. North 

 America: Timber Map, No. 2. South America: 

 Timber Map, No. 3. Europe and Africa: 

 Timber Map, No. 4. All prepared by J. Hudson 

 Davies. Each on rollers, size 40 in. by 30 in. 

 (Edinburgh : W. and A. K. Johnston, Ltd. ; 

 London : Macmillan and Co., Ltd., n.d.) Price 

 85. net each. 



(i)pvR. BOERKER'S book is a popular 

 L/ account of the administration and pro- 

 tection of the national forests of the United States, 

 which now constitute about a tnird of the timber 

 lands in that country. The original forest area was 

 enormous, being estimated at 850,000,000 acres. 

 Nearly half of this has been cleared away, as the 

 land was needed for farms by settlers ; but forest 

 fires, felling for timber, and grazing have shared 

 largely in the destruction. To-day the land under 

 timber trees is about 500,000,000 acres. Private 

 ownership entailed disappearance of the forests, 

 as no steps were ever taken to provide for the 

 growth of a second crop of trees upon the ground. 

 State intervention became necessary, and nothing 

 in the political history of the United States is more 

 creditable than the legislation of late years enforc- 

 ing measures to preserve from fire and to manage 



