July 5, 1906] 



NA rURE 



219 



China, the rang-e of spring tides is about twelve feet 

 at the nioutli; but the tidal wave becomes compressed 

 in advancing; towards the head of the estuary, and 

 reaches twenty-five feet in height at ordinary springs 

 and thirty-four feet when an onshore gale is blowing. 

 The bore is said to enter the river at the rate of 141 

 miles an hour, and during the first hour the rise of 

 tide is ten feet. Its api)roach can be heard for a 

 distance of fourteen or fifteen miles. The Severn bore 

 is too well known to need description. Its height has 

 been estimated at three to four feet, and velocity at 

 seven to eight miles an hour. 



In another section the author deals with wave motion : 

 first with wind waves and secondly with seismic and 

 cyclonic storm waves. As a civil engineer, his chief 

 interest is with the effects of wave motion upon harbour 

 works, coast defences, and other constructions ; but 

 these chapters also give an excellent summary of the 

 theory of deep-sea waves and the results of observ- 

 ations on their dimensions and speeds. Some of the 

 facts recorded as to damage done by wave action are 

 very striking. During the construction of Plymouth 

 breakwater, blocks of stone weighing from seven to 

 nine tons were carried over the top through a distance 

 of 138 feet and deposited inside the brealcwater. .\t 

 Bilbao a solid block of the breakwater weighing 1700 

 tons was overturned. The partial destruction of the 

 north pier at Tynemouth furnishes another illustration ; 

 in that case there can be no doubt that the depth below 

 still-water level to which wave disturbance was likely 

 to go in that locality had been consideratly under- 

 estimated. As to earthquake and cyclonic waves, Mr. 

 Wheeler has collected a large amount of information 

 of an interesting character, and he deals at some 

 length with " solitarv " ocean waves, which he thinks 

 are chiefly due to submarine disturbances. The great 

 majoritv of the solitary waves that have been observed 

 in the North .Atlantic were in a line between places 

 subject to volcanic activity. One of the latest examples 

 of the destructive effect of a solitary wave occurred 

 in October, 1905, to the Cunard liner Campania on 

 her outward vovage to New York. A fresh gale 

 was blowing on the Grand Banks of Newfoundland 

 when the ship was suddenly struck by an enormous 

 wave ; she lurched over, the water swept over the 

 deck several feet deep, five passengers were washed 

 overboard and twenty-nine others seriously injured. 

 This wave was said to have reached as high as the 

 funnels, but in the circumstances accurate estimates 

 could hardly have been made. 



The final chapter deals with tides as a source of 

 power. The author gives full accounts of applications of 

 the principle that have been made at various times, but 

 his conclusion is that the attempt to utilise tides on a 

 large scale with existing mechanical appliances cannot 

 be considered as coming within the lines of commercial 

 economics. In this conclusion he has the support of 

 general engineering opinion. 



On the whole. .Mr. Wheeler has succeeded in the 

 object he had in view, and has " produced a handbook 

 that will be of interest and practical service to those 

 who have neither the time nor the opportunity of in- 

 vestigating the subject for themselves." W. H. W. 

 NO. 1914, VOL. 74] 



ELECTHUliy METERS. 

 Electricity Meters. A Treatise uii the General Prin- 

 ciples, Construction, and Testing oj Continuous 

 Current and .Mternating Current Meters for the Use 

 of Electrical Engineers and Students. By Henry G. 

 Solomon. Pp. x-l-323. (London : Charles Griffin 

 and Co., Ltd., igo6.) Price i6s. net. 

 1 ]NTIL a few months ago the literature on the 

 ^ subject of electricity meters was entirely con- 

 fined to articles in text-books on electrical engineer- 

 ing, and the advent of a bock dealing exclusively 

 with this subject is therefore a matter of import- 

 ance to tho.se interested in the distribution of elec- 

 trical energy. In the book just published by Messrs. 

 Griffin, Mr. H. G. Solomon has written a clear and 

 comprehensive treatise on the principles and construc- 

 tion of this most import.int piece of electrical ap- 

 paratus. 



The first chapters are introductory, and deal mainly 

 with the theory of action of the more important 

 types. In chapter ii. an important section on the 

 behaviour of three-wire energy meters is deserving 

 of attention. The errors in reading due to want 

 of balance, both as regards pressure and current 

 on a three-wire system, when the shunt coils of a 

 three-wire meter are connected respectively across 

 the outers, and between the middle wire and the 

 outer, have been worlied out. In the appendix 

 figures are given which show the percentage error 

 in different cases, and the advantage of connecting 

 the shunt coil directly across the outers is clearly 

 proved. The fact that there is any error at all with 

 this arrangement has hardly been recognised, though 

 for switchboard meters the matter is certainly one 

 of importance. The following chapters contain de- 

 scriptions of the various types of iquantity and energy 

 meters for continuous current circuits, and are largely 

 reminiscent, as writing of this kind must always be, 

 of manufacturers' pamphlets. 



Mr. Solomon has very wisely excluded all his- 

 torical and out-of-date meters from this part of his 

 book, and the section contains a clear description, 

 fully illustrated by many e.xcellent drawings, of the 

 meters which the central station engineer has to use 

 and to test. The author is to be congratulated on 

 having almost entirely eliminated illustrations of the 

 outer cases of the instruments which he describes, 

 a type of illustration, unfortunately, all too common 

 in some other works on kindred subjects. Chapter vi. 

 contains a description of continuous meters for special 

 purposes. The last section deals with tramcar meters. 

 The practical importance of this type of meter is 

 hardly yet well recognised. .As Mr. Solomon says : — 

 " The careless manipulation of the controller and 

 brake is a matter of .serious importance, resulting 

 in a considerable loss of energy. By properly re- 

 cording the actual energy taken by the cars, and 

 keeping records of the motor men, a saving amount- 

 ing to from to to 20 per cent, of the total used can 

 be effected." The descriptions of the best known 

 tvpes of meter for this purpose are somewhat disap- 

 pointing. 



