49: 



NA TURE 



[October 21,1 909 



would sur\i\e if returned to the sea. The experi- 

 ments were conducted with both otter- and beam- 

 trawls, and show that fish from long- hauls of the 

 trawl are much less likely to survive than those from 

 short hauls, and that the otter-trawl, which is now 

 practically exclusively used by steam trawlers, inflicts 

 much more serious injury on the fish than does the 

 beam-trawl. The effect of exposure of the fish on 

 the deck of the vessel for different periods of time 

 has also been studied. 



Dr. W. Wallace writes on the subject of the size 

 and age of plaice at maturity. The method used for 

 determining age has been the examination of the 

 otoliths or ear-stones of the fish, the alternate dark 

 and white rings of which form a record of seasonal 

 growth. The most striking result of Dr. Wallace's 

 work is the determination of the fact that the average 

 size and age of plaice at first maturity varies in 

 different regions. In the central part of the North 

 Sea, around the Dogger Bank, female plaice are, on 

 the average, 16 inches long, and the majority are 

 just six years old when they become mature for the 

 first time. In the southern bight of the North Sea 

 the average size of the females at first maturity is 

 only 13 inches, and the age five years; in the western 

 part of the English Channel the average size is about 

 the same as in the southern North Sea (\y inches), 

 but the average age is four years instead of five, 

 owing to the more raoid growth of the young plaice 

 in the Devon bays. Similar differences are found for 

 the male plaice also, which mature at a smaller size 

 than the females. 



The report on records of catches furnished bv the 

 captains of Lowestoft sailing-trawlers, which is 

 written by Miss R. M. Lee, shows the value of such 

 records provided bv fishermen in supplementing and 

 extending the work done bv the scientific steamers. 

 The area worked over by the Lowestoft men corre- 

 snonds roughlv with the southern bight of the North 

 Sea. The analysis of the figures, which Miss Lee 

 has been able to make, indicates that in the northern 

 nart of this region pl.nice occur in maximum quantity 

 bv weight during the summer and in minimum 

 quantity during the winter months. In the southern 

 part of the area, on the other hand, the maximum 

 is in winter and the minimum in summer, whilst in 

 the intermediate region there are maxima in spring 

 and autumn. These records, therefore, clearly con- 

 firm the southward mipration of plaice for the pur- 

 pose of spawning in winter, whicli marking experi- 

 ments in this part of the North Sea had already fore- 

 sh.adowed. 



.'Vn account of the hydrographical investigations in 

 the English Channel for the years 1904-t; is con- 

 tributed by Mr. D. J. Matthews, and is illustrated 

 by a series of very valuable plates, which set forth 

 the results in graphic form by means of coloured 

 charts and sections. The importance of these hydro- 

 graphical investigations in the English Channel in 

 connection with the problems of North Sea fisheries 

 can scarcely be exaggerated, since the Atlantic water 

 which reaches the southern area of the North Sea 

 comes practically exclusively by way of the English 

 Channel. In both the years 1004 and iqoj the 

 salinities in the English Channel reached a maxi- 

 mum in the early months of the year, and fell to a 

 minimum in the summer. The evidence indicates, 

 further, that the movements of the water were more 

 frequent and raoid in 1004 than in 1905. Special 

 attention was given to the conditions prevailing at 

 the mouth of the English Channel, where the two 

 conflicting currents already demonstrated in 1003 

 were again encountered, a low salinity current flow- 

 ing southwards from the Irish Channel across the 

 mouth of the Enfflish Channel, and a current of 

 NO. 2086, VOL. 81] 



high salinity entering' the Channel from the south- 

 west. 



The volume, as a whole, contains a large mass of 

 data of the greatest importance for the solution of 

 many of the problems dealing with marine life, and 

 more particularly Vi'ith the natural history of fishes. 

 It must be borne in mind, however, that it is essenti- 

 ally a contribution of data to the much wider and 

 more comprehensive scheme of investigation which 

 is being carried out in connection with the Inter- 

 national Council, and not until the whole work 

 which the various countries have done has been 

 brought together and the results duly correlated can 

 the full fruit of these researches be gathered. 



DOUBLE-STAR STUDIES.^ 

 A COMPLETE record and discussion of the double- 

 *^ star measures made at the Potsdam Observatory 

 by Prof. Lohse, the director, during the period 1899 to 

 1908 is given in Publication No. 58 of the Observa- 

 tory. Prof. Lohse employed a refractor made by 

 .Schroeder about twenty-five years ago. The objective 

 is eleven inches, and the flint is dark green. It may 

 be described as a good instrument, but not of the 

 highest quality. Nevertheless, we notice that Prof. 

 Lohse was able to secure measures of some difficult 

 pairs, notably S Equulei, k Pegasi, and Sirius. The 

 filar micrometer has one fixed and one movable thread. 

 Generally the power employed was 550, but occasion- 

 ally one of 800 was used. The power ordinarily used 

 with the Greenwich 28-inch refractor is 670, and 

 occasionally 1120. Setting out with a definite pro- 

 gramme, lie chose a working list of 166 double stars 

 made up of known binaries and others of interest, 

 and during the nine j-ears he was making measures 

 of these systems he collected those made by other 

 observers, and hence was in a position to make a 

 useful discussion of his results. 



The present volume is therefore divided into tvi'o 

 portions. Part i. contains the measures made at 

 Potsdam, and part ii. their discussion in combination 

 with measures made since the discovery of each pair. 

 Prof. Lohse uses the method of Zwiers to determine 

 his orbits, and discusses altogether thirty. The actual 

 elements arrived at in most cases differ little from 

 previous orbital elements, and do not call for special 

 remark, except, perhaps, in the cases of tj Cassiopeiae 

 and 70 Ophiuchi. The apparent orbit given for rj 

 Cassiopeise does not seem the most suitable, and 

 brings out a period of 345 years, or 100 years larger 

 than that generally accepted. In the case of 70 

 Ophiuchi, Prof. Lohse has done a good piece of work 

 in attacking one of the anomalies often found in 

 double-star orbits. It is found that the differences 

 between the computed and observed jjositions of the 

 companion tend to periodicity. This may be due to 

 some fault in the gravitational theory, to errors due to 

 personality, or to the effect of some disturbing body. 

 The binaries C Herculis and 70 Ophiuchi are excellent 

 examples of this, and Prof. Lohse, who favours the 

 personality explanation, has taken great pains to com- 

 pute the relative areas swept out by the companion to 

 70 Ophiuchi every six months, and obtains figures in 

 agreement with those deduced by quite independent 

 methods. He is, however, unwilling to admit the 

 reality of the figures, and remarks that by a judicious 

 selection of observations the deviations from the law 

 of equal areas may be reduced. This is the method 

 advocated by Prof. Burnham, but it is not easy to 



1 Piiblikationen des Astrophy^ikalischen Observatorlums zu Potsdam, 

 No, 58. Z^vanzigsten Bandes, Erstes Stiick. DoppeUterne von O. Lohse 

 (Director). Pp. i68. (Potsdam, 190S ; in Kommission bei W. Engelmann 

 in Leipzig.) 



