i i inclination. 



231 



b. Hydrographical Notes. 



In the first part of this work, a number of hydrographical 



data from the fiords will be found. Now I will mention a few 

 more details, and treat of some things which have not yet been 

 mentioned. First then, some remarks on the influence which the 

 prevailing winds, waves and tidal currents exert on vegetable and 

 animal life in the sea. 



In a very interesting paper. Mr. F. W. Hak.mkk has recently 

 explained the importance of the prevailing winds as a geological 

 factor. 1 ) Mr. Habmeb calls attention to the fact that dead shells 

 are not found in large numbers on the eastern shores of the 

 counties nf Norfolk and Suffolk, although there is no want of mol- 

 luscs in the adjacent sea. The reason for this absence of shells 

 is found by .Mr. Hak.mkk in the fact that the prevailing winds at pre- 

 sent are westerly. * hi the contrary, the presence of Crag beds on 

 the east coast presupposes a different prevailing wind from that 

 which is now the case. 



„Easterly gales might have been prevalent in that part of the 

 North Sea. rather than those from a westerly quarter, as at pre- 

 sent." In another paper. Mr. Hak.mkk-') has drawn attention to 

 the tidal currents as a geological factor. 



He points to the state of things in the Irish Sea. ..where an 

 accumulation of dead shells on the Turbot bank, off the coast of 

 Antrim, is caused by the tidal currents which sweep with much 

 velocity through the narrow channel separating Ireland from Scot- 

 land." The fact that in some places in Coralline Crag, layers of 

 large shells may occur, while at other places smaller shells are 

 predominant, is considered in the light of tidal currents, for Mr. 

 Habmeb says: -- „Shells are sorted out by currents of varying 

 strength as pebbles in beds of gravel; small specimens would there- 

 fore have accumulated in one place, larger ones in another, and 

 comminuted shells, or tine calcareous sand in a third." 



Wind and current are not of little importance in dynamical 

 geology, on account of Jbeir carrying power, lint just this charac- 

 teristic causes these factors also to have an influence, in different 

 ways, upon living creatures. The course of a current offers par- 

 ticularly favourable conditions for the nourishment of plankton- 

 eaters, and a current-facies of animals may be spoken of. It is 

 true that animal life is not profuse where the deposits of material 

 are greatest, but. on the whole, it is correct to say that the bed of 

 a current is profusely supplied with animal life. 



In a purely theoretical light, the supply of plankton for a given 

 animal must be in proportion to the velocity of the current. It is, 

 at any rate, evident that the motions of the water are of great 

 importance in connection with the supply of nourishment for plank- 

 ton-eaters. 



Dr. Edwabd Hkownk :; i has drawn attention to the fact that 

 medusae, which are kept in an aquarium where the water is un- 

 disturbed, will at first swim quickly about. ..but in a kw hours, it 

 sinks to the bottom, apparently tired out. After an interval of 

 rest, it takes another swim, and again sinks to the bottom. This 

 is repeated until the medusa becomes exhausted; then it stays at 

 the bottom and slowly dies.' - This unfortunate state of things has 



q Influence of Winds upon Climate during tin' Pleistocene Epoch Quart. 

 Journ. Geol. Soc, vol. LVII, 1901, p. 408. 



-) A Sketch of the later tertiary History of Easl Anglia. Eroc. Geol. 

 Assoc, vol. XVII, 1902, p. 425. 



3 ) On Keeping Medusae : live in an Aquarium. Journ. Mar. Biol. Assoc, 

 N. S. Vol. V, no. 2. 1898. 



been remedied by Dr. E. T. Beowne and Dr. E. I. Allen having 

 succeeded in constructing an apparatus by means of which the 

 movements of the water have been skilfully imitated. Mr. Danne- 

 vig's hatching apparatus is constructed on a similar principle. 

 With regard to the force of the tidal currents, it will easily be 

 seen that this will depend upon the height of the tide, i. e. the 

 difference between ebb and flow. In the north of Norway, this 

 difference is. on an average, about 2 mtrs., and as a consequence 

 of this, the tidal currents are considerably strong in the narrow 

 channels and in the smallest parts of the fiords. Rased upon 

 material furnished by the Norwegian ..Gradmaalingskommission", 1 ) 

 I will give some figures which show the average difference between 

 high and low tide in succession in 1884 and 1885. 



1884. 1885. 



Stavanger 0.424 m. 0.427 m. 



Bergen 0.988 .. 0.97:. .. 



Kabelvaag 2.o4n „ 2.014 .. 



Vardo 2.195 „ 2.175 „ 



Generally speaking, it may be said that the tidal wave runs 

 northwards along the coast, and the tidal currents flow into the 

 fiords when the tide rises and outwards when it falls. 



In the channels of the M skjsergaard", it may be taken as a 

 general rule, that the direction of the current is northerly or 

 easterly when the tide rises, westerly or southerly when it falls. 

 But it must be remarked that in many channels the direction of 

 the current changes a little after the water has been at its highest 

 and lowest. In the currents running between the islands of Lofoten 

 (Gimsostrom, Napstrom, Sundstrom etc.) the water at first flows 

 northwards when the sea is at half-high-tide and turns again at 

 half-low-tide. The same is said to be the case in the currents 

 which connect the Skjerstad and Salten Fiords. The best known 

 of these is the socalled ..Saltstrom". which surpasses even ,,Mosken- 

 strommen" in force. 



I have attempted, in an article on the two mael streams in 

 Norway, ide to store malstromme i Norge) 2 ) to explain the change 

 in the direction of currents at half-high and half-low-tide, and have 

 theoretically worked out the following conclusion: - - If the inner 

 part of a fiord be connected by a current with the principal fiord, 

 and the direction of this current be changed after high and low 

 tide, the difference between ebb and flow will be less inside than 

 outside the said current. 



Thus, the difference between the niveau at high and low water 

 should be less in the Skjerstad than in Salten Fiord. I have not 

 as yet had an opportunity of verifying this theoretical conclusion. 



Concerning the direction of the surface stream alono- the coast 

 of Norway, Mohn's current map is very instructive."! The fol- 

 lowing amusing little story shows that there, in the summer, may 

 be an easterly current along the coasts of Finmarken. Sokhks 

 Teomholt 4 ! relates that in the beginning of the eighties S/S. 

 „Nordstjernen" was in the summer wrecked on Knivskja?lodden, a 

 little west of the North Cape, and very soon sank. A couple of 

 months later, the vicar of Naesseby had rowed out a little way in 



'i Cf. Vandstandsmaalinger, h. IV. p. 124. 



2 ) „Naturen" L901, p. 305. 



3 ) The North Ocean, pi. XLIII. 



*) Under Nordlyseta Straaler, p. 557. Copenhagen 1885. 



