Jan. 13, 1887] 



NA TURE 



24: 



called the " progressive " principle— that is, at a number 

 of different speeds from the maximum speed attainable 

 down to four or five knots per hour — are of the greatest 

 value to future designs of ships and machinery. For a 

 long time they have been made occasionally in the Ad- 

 miralty practice ; but Mr. \V. Denny deserves great credit 

 for bringing the system into general use and establishing 

 its practical value. Associating progressive trials with 

 the " law of comparison " for the resistances of ships of 

 different dimensions but similar forms, a designer can 

 feel great confidence of success in most of his practice. 

 If he has the data for small ships propelled at relatively 

 high speeds, he has the means of approximating closely 

 to the performances of larger ships up to much higher 

 speeds, and this is of enormous value under present 

 conditions. 



Methods oi propulsion and details oi propellers occupy 

 a large section of the volume under review. The paddle- 

 wheel, the screw, and the water-jet propeller all receive 

 full discussion in their theoretical and practical aspects. 

 Probably no such summary of facts relating to modern 

 practice has been made before by any writer. Under 

 paddle-wheels, for example, there are descriptions con- 

 stituting practical data for designing paddles at the sides 

 of steamers (the ordinary plan), at the stern, as in light- 

 draught river-steamers, and at the centre, between twin_ 

 hulls, as is the fashion in some American river-steamers . 

 Under the jet-propeller appears a great mass of informa- 

 tion as to the fittings and performances of a number of 

 vessels, including the English gunboat W'aterivitch and 

 Thornycroft's torpedo-boat of recent construction, the 

 German Hydrofnotor, described in Natxjre, vol. xxvi. pp. 

 18 and 247, and a Swedish experimental boat. Naturally 

 the greatest attention is bestowed upon screw-propellers, 

 which are most generally employed. To the theory of 

 the screw-propeller laid down by Rankine, many valuable 

 additions have been made by the Froudes, father and 

 son, Mr. R. Froude being still engaged in the investiga- 

 tion of the subject experimentally. Up to the present, 

 however, it cannot be said that any complete, acceptable 

 theory has been put forward. Experience shows that by 

 the choice of proper screws enormous economies of 

 power or sensible increases in speed may be secured. 

 The first trials of H.M.S. Iris, nearly ten years ago, were 

 fortunately most disappointing, for they compelled a close 

 study of the screw question in her case, with the result 

 that the speed was increased from i6i to iSA knots per 

 hour simply by a change of screws. Similarly striking 

 results have been obtained in ships and boats of the 

 torpedo flotilla, and in vessels of the mercantile marine. 

 Much yet remains to be done before a satisfactory prac- 

 tice can be insured in choosing a suitable propeller for a 

 ship of novel type or exceptional speed. Probably here 

 also experiment with models of screws will come in to 

 assist full-scale operations. Attempts in that direction 

 have been made for many years past in the Admiralty 

 Experimental Works, but the task is one of great dehcacy 

 and difficulty, and is far from having been completed. 



Mr. Busley goes over this ground very carefully, and 

 gives practical rules, based on experience for the most 

 part, for fixing the sizes and pitch of screws. One of the 

 best of these is that published by Mr. S. Barnaby and 



based on the extensive experiments of the Messrs. 

 Thornycroft, whose success in the construction of excep- 

 tionally swift vessels results in part from the close attention 

 given by them to screw-propellers. Mr. Busley has an 

 interesting chapter on the geometry of screw-propellers ; 

 and his remarks on the most suitable materials for pro- 

 pellers are important. 



The illustrations to this volume are numerous and well 

 executed. The letterpress and general style of produc- 

 tion leave nothing to be desired. It may be anticipated 

 that the work now completed will speedily become a 

 standard book of reference for German marine engineers. 



W. H. W. 



AN ARCTIC PROVINCE 

 An Arctic Province : Alaska and the Seal Islands. By 

 Henry W. Elliott. Illustrated by many Drawings frora 

 Nature, and Maps. (London : Sampson Low and Co. 

 18S6.) 



MANY accounts of Alaska and of the wonderful 

 seal-rookeries to be met with on some of the 

 islands in its Arctic seas have been published, but none 

 which have given in so interesting and succinct a man- 

 ner the history of these far-off northern solitudes as the 

 present volume. The author's personal knowledge of 

 these regions, and his intimate acquaintance with the very 

 numerous writings of others on the subject, have enabled 

 him to write a volume that will long remain a standard 

 one ; while the illustrations from his own pencil are full 

 of life and vigour, and add immensely to the value of the 

 work. 



The volume contains, of course, an account of the 

 discovery, in 1 741, of the Alaskan Province by Veit Bering, 

 and of his shipwreck and sad death. The survivors 

 spread the news of the wealth of fur and ivory that was 

 to be found there, and soon came the rush of Russian 

 traders. Fierce struggles took place between the in- 

 dividual traders and the natives, and much blood was 

 shed, but at last a Russian American Company was 

 established with supreme powers ; and for a time, under 

 the supervision of that very remarkable man. Governor 

 Alexander Baranov, it flourished. Its decadence, how- 

 ever, proved to be as rapid as its rise ; and after various 

 vicissitudes, lasting during the first half of the present 

 century, the district was, in 1867, acquired by the United 

 States Government by negotiation from Russia. The 

 name of Bering was given to the Straits connecting the 

 Pacific with the Arctic Ocean by our Capt. Cook. 



The features of the Sitkan region are treated of in a 

 special chapter. Were it not for the damp and extensive 

 rainfall, the climate would be endurable. Agreat dealof the 

 scenery is most picturesque. The aboriginal life of the 

 Sitkans is glanced at, but this portion of the work con- 

 tains nothing very new or profound, as the author does 

 not profess to know as much about the natural history of 

 the human race as about that of the marine mammalia. 

 In separate chapters, the alpine zone of Mount St. Elias, 

 Cook's Inlet and its people, and the great Island of 

 Kodiak, are treated of. The quest of the otter has a 

 whole chapter devoted to it. Few ladies realise how 

 many men are engaged in deeds of hazardous peri! 



