May 1 1, 1905J 



NA TURE 



45 



FISHERY INVESTIGATIONS IN THE 

 NORWEGIAN FJORDS.' 

 "P) R. NORDGAARD has collected the results of investi- 

 ^^ gations made in some of the fjords of northern 

 Norway in the winters of 1899 and 1900, during the course 

 of researches in the fishing waters of Lofoten, carried out 

 at the expense of the Bergen iVIuseum and the Norwegian 

 Government. Two " expeditions " were made. The first, 

 January to May, 1899, included the Vest Fjord and the 

 sea beyond Lofoten, Vesteraalen, Sengen, and Finmarlven, 

 besides a large number of fjords, as the Kirk, the 0gs, 

 the Kanstad, the Sag, and many others. The second, in 

 the winter of 1900, was made so as to obtain material 

 from the fishing banks which would compare with that of 

 the previous year, and it included visits to the Morsdal, 

 Salten, Skjerstad, and Folden fjords. 



The hydrographical observations, which are numerous, 

 have been made according to recognised standard methods, 

 and are therefore comparable with observations made 

 further out at sea, in the regions in which the full ex- 

 planation of many of the facts brought to light here is 

 doubtless to be found. The chief hydrographical result 

 arrived at by Dr. Nordgaard is that the northern fjords 

 can be divided into two groups, those in which the bottom 

 temperature is 6° C. to 7° C., and salinity about 35 pro 

 luiUcj and those in which the bottom temperature is below 

 6° C, and salinity less than 35 pro mille. As examples of 

 the former, the Salten, Folden, Tys, Ofot, and Vest fjords 

 are given, and as examples of the latter the Malang, 

 Lyngen, Kvaenang, Porsanger, Tana, Varaanger, Skjer- 

 stad, Skjomen, Kanstad, 0gs, and Kirk fjords. It is 

 suggested that while in some cases, as the Skjerstad 

 fjord, the inflow of ocean water is cut off by a submarine 

 ridge, the occurrence of the two typical groups may be 

 accounted for by the distribution of rainfall. The heavy 

 winter rainfall in western Norway affords a largo supply 

 of fresh water to the surface layers of the fjords, which 

 accordingly remain specifically light, notwithstanding the 

 fall of temperature. In northern Norway the rainfall is 

 much less, hence the surface waters retain a high salinity, 

 and as their temperature falls they sink to considerable 

 depths. 



Dr. Nordgaard also discusses at some length the vary- 

 ing influence of different amounts of rainfall on the currents 

 within the fjords. Heavy rainfalls, which raise the sur- 

 face level of the water, are for the most part the result 

 of winds from the ocean, which produce a similar effect ; 

 it is difficult to separate the effects of the two causes, but 

 a rainfall above the average is taken as a fairly certain 

 index of abnormal strength in the oceanic streams. 



In the " biological notes " which accompany the tables 

 a number of points are brought out showing and defining 

 the connection between fauna and hydrography. It is 

 shown that whereas in the first or warm-water group of 

 fjords the deep-water fauna is chiefly boreal, in the second 

 group, where cold water of loviJer salinity makes its way 

 downwards, the predominant forms are Arctic. The effect 

 of the increased precision of modern methods of investi- 

 gation in greatly reducing the number of so-called cosmo- 

 politan species is also emphasised. 



The section of this memoir which deals with fisheries 

 is specially important and suggestive. In discussing the 

 Lofoten fisheries. Dr. Nordgaard adopts the view that the 

 currents in the Norwegian Sea are controlled by the 

 winds, and that, as already explained, abnormal move- 

 ments of the currents off-shore or on-shore can be associ- 

 ated with rainfall above or below the average. Again, 

 he says, " It is clear that during the movements to or 

 from the coast of the surface water, a compensating current 

 must be set in motion in the deep water ; it has long been 

 a recognised phenomenon in the fjords, that the surface 

 and under currents go in contrary directions." From an 

 examination of the observations. Dr. Nordgaard concludes 

 that herrings move coastwards specially in the surface 

 layers, while the cod travels along in the deeper layers. 



^ Bergens Museum. *' Hydrographical and Biological Investigations in 

 Norwegian Fjords." By O. Nordgaard. " The Protist Plankton and the 

 Diatoms in Bottom Samples." By E. J*rg;nsen. Pp 254 ; with 21 plates 

 and 10 figures in the text. (Bergen : John Grieg, 1905.) 



It must therefore, he continues, " be supposed that as cod 

 and herrings, to a certain extent, depend upon contrary 

 current phases, a particularly good spring herring fishery 

 would prevent a correspondingly good cod fishery in the 

 saine district ; for a strong tendency of the upper layers 

 towards the coast certainly takes herrings along in the 

 current, but this at the same time causes a compensation 

 current in the deep water, and this current hinders the 

 cod in its passage to the spawning places." 



The statistics of the yield of the cod and herring 

 fisheries for some years are discussed and compared with 

 corresponding values of rainfall, with results which appear 

 to support the hypothesis brought forward. It would of 

 course be easy to suggest difliculties, such as the ex- 

 tension of the current regime observed in fjords to areas 

 which can hardly be regarded as such, and may there- 

 fore have a different system of movements. But as 

 the whole question is at present under investigation on the 

 large scale by the International Council, we content our- 

 selves with an attempt to sunmiarise Dr. Nordgaard's 

 results, deferring fuller discussion of them until the more 

 abundant data are available. 



A NEW SLIDE RULE. 



A/I ESSRS. JOHN DAVIS AND SON, of Derby, the 

 well known instrument makers, are bringing out a 

 variation of the slide rule which is likely to increase its 

 value for certain classes of calculation without interfering 

 with the simplicity and convenience of the form with which 

 we are all familiar. The lower groove on the outside of 

 the rule, which ordinarily is only wide enough to hold 

 the inturned edge of the cursor, is made wider, so as to 

 take one of the tongues of a spare slide, and this slide 

 is held in place when required by two light aluminium 

 clips which grasp the ends of the rule and of the spare 

 slide while leaving the usual slide free to move. An 

 extra cursor is also provided which is long enough to 

 grasp both the rule and the extra slide. By this means 

 any rare or special scales upon the extra slide are for the 

 time being equivalent to scales upon the rule, and these 

 may be read against scales upon the other slide by means 

 of the long cursor. If desired, the extra slide can take 

 the place of the ordinary slide, or may be removed 

 altogether when the rule, if provided with an ordinary 

 cursor adapted to the altered lower groove, becomes an 

 ordinary slide rule. In the example submitted, the extra 

 slide carries what are called E and — E scales. The E 

 scale is a log log scale, and is always being re-invented ; 

 it was called a P line or power line by Lieut. Thomson, 

 who showed it at the Inventions Exhibition, and it was 

 long before invented by Dr. Roget. This P or E line is 

 very handy, for it at once enables the logarithm of any 

 number on any scale, i.e. to any base, to be read accord- 

 ing to its position against an ordinary A line, while frac- 

 tional or high powers of numbers are read with equal 

 facility. Compound interest, pressures and volumes of 

 gases under isothermal or adiabatic conditions are readily 

 evaluated with the aid of the E line read against an A line. 

 If, however, a pair of E slides are used, one in the usual 

 position and one attached below the rule by means of the 

 clips, then against any value, say of -j, on one. the cursor 

 will show the value of vy on the other, 7 having any 

 desired value according to the relative position of the two 

 slides. 



The slide rules made by Messrs. Davis and Son are too 

 well known for their accuracy and finish for it to be 

 necessary to refer more to such points, but by some curious 

 perversity or accident there is one little fault in the rule 

 sent for examination which only needs to be pointed out 

 to be put right. On the feather edge a scale of inches in 

 i6ths is provided ; on the lower face outside the rule there 

 is no scale at all, while inside, to be used like a hat 

 measure, there is a scale of millimetres beginning at 550. 

 If, therefore, the rule is required for the prosaic but very 

 useful purpose of measuring a length, this can only be 

 measured in inches if it is 20 inches or less, or in milli- 

 metres if it lies between 550 and 1040 millimetres. If, 



NO. 1854, VOL. 72] 



