[une 26, 1884] 



NA TURE 



205 



Tromso. On this point, too, we are without conclusive proofs, 

 but the examinations have, as already stated, been extended 

 inwards to the mouth of the Balsfjord and its environs, and the 

 results of these disprove such an assumption. Granite blocks 

 are thus to be found about the mouth of the Balsfjord, but in 

 far lesser numbers than over the Troms Island. It is just on 

 the southern part of this island that travelled blocks are found 

 in largest numbers in the whole district ; while the circumstance 

 that neither blocks nor fragments of Saussurite gabbro, which, 

 as pointed out, are found in enormous quantities in the neigh- 

 bourhood of the Bal fjord, can be discovered among the tra- 

 velled blocks on the Troms Island, further corroborates my 

 belief that no transport of blocks from the Balsfjord outwards 

 to the sea has taken place. In fact, I am fully convinced 

 that the block-tran-port has taken place from the coast inwards. 



There is thus every reason to believe that the travelled granite 

 blocks have not been carried out to the Troms Island through 

 I he Balsfjord. In fact, there seems more probability that the 

 transport was effected through the Mails River. But, if this 

 was so, travelled granite blocks would have been found on the 

 slopes of the Malang, and here too in decreasing numbers from 

 the inland towards the outer islands, which appears, h iwever, 

 not to be the case. I have therefore come to the conclusion that the 

 birthplace of the travelled granite blocks in the vicinity of Tromso 

 must be referred to the gneiss-granite stratum of the coast, and 

 thus again chiefly to that part of the same which appears at the 

 Kval and Ringvats Islands west of Tromso. This assumption 

 is supported too by the circumstance that a great number of the 

 travelled blocks, judging by the petrographic composition of the 

 mountains in que>tim, undoubtedly belong to the gneiss-granite 

 of the coast, and that there is nothing to disprove the theory 

 that even the blocks which petrographically seem to differ in 

 composition also belong to the same stratum in composition. 



The highest elevation in which the travelled blocks are found 

 in the neighbourhojd of Tromso indicates that the transport of 

 the same has taken place after the close of the Glacial period, 

 i.e. in an age when the continuous layer of the Ice age had 

 broken up into more or less separated glaciers. Under these 

 circumstances the transpDit of the blocks from the Kval Island 

 inwards to the Troms Island must have been effected by floating ice. 

 The highest line of elevation in which the blocks along the 

 sounds are deposited indicates, therefore, the height of the sea at 

 the commencement of the block-transport. And as the blocks 

 are often found in greatest number somewhat below this line, I 

 have come to the conclusion that block-transport has progressed 

 more rapidly as this period advanced. I may, however, add 

 t! at the whole epoch of the block-transport has probably been 

 a short one. 



The local c mditions of Kval Island seem also to have greatly 

 fwoured even the most extensive block-transport at an early age. 

 The continuous layer of ice of the Glacial period has thus, as 

 demonstrated above, been broken up thus early, that the ice 

 remained only in local glaciers of great extent. So early must 

 the block-transport have taken place also in an easterly direction, 

 1 10th through open channels of the Balsfjord and the Kval Sound, 

 and unimpeded by the ice-streams moving down from the main- 

 land. V. hen, however, this, as appears from the blocks in the 

 neighbourhood of Tromso cannot have been the case, at all 

 events to a limited extent alone, there is herein an obvious proof 

 that special conditions which favoured the current carrying the 

 blocks to the shore did not exist before the epoch which corre- 

 sponds with the highest level in which the blocks are found. 



If the blocks « ere, as I believe is demonstrated beyond doubt, 

 transported to their places by fl rating ice, the flow of the curre ts 

 must have greatly influenced the direction of the block-transport. 

 At a period, therefore, which is determined by the transport 

 commencing eastwards, special conditi 111s must have existed 

 \ihich hive caused a stronger flow of the current from the outer 

 cjast inwards. There are, in fact, several circumstances which 

 s-eem to point in this direction. There is in particu ! ar that of 

 the Gulf Stream. It is thus evident that the Gulf Stream, 

 which during the Glacial age was diverted from the coast of 

 North Norway, has, in a comparatively recent era, curved 

 t iwards the coast to a considerable extent. 



As is generally known, a complete Arctic Sea fauna existed 

 al m; the coast of Norway in the early part of the Quaternary 

 age ; but by degrees this has been more and more mixed with 

 southern species, an encroachment which c mtinued without 

 interruption to the preseut time, and is, I believe, still in full 

 operati in. Some perfectly pure species of the Arctic fauna may 



still be met with in some of the deepest fjords of Norway, but 

 even these remains are mist probably in retrogression. This 

 constant retrogression of the original Arctic Sea fauna on the 

 coast, and the encroachment of a more southern, must naturally 

 be dependent on currents of warm water coming from the south, 

 and as long as the Arctic fauna alone supervened, these warm 

 currents must have been entirely absent from the coast line 

 referred to in this paper. From the moment access was made 

 forthesam*, the sDUthern fauna began to manifest itself. In 

 the block-transport here described, which began at a period 

 when the surface of the sea lay, in relation to the fundamental 

 rock, about 30 m. higher than at present, I believe we may find 

 a more exact determination of the time when this curve in the 

 current took place. 



There is, besides this circumstance, another of equally great 

 importance which points in the same direction. It is a fact, 

 thus, that fragments of pumice-stone are constantly washed 

 ashore on the coasts of North Norway, and even on those of 

 the Polar lands as far as the Gulf Stream reaches, but pumice- 

 stone is not found at any elevation in Northern Norway, but only 

 a.' the lowest by the shore. In fact, the highest line al mg which 

 pumice-stone is found here c dncides nearly exactly with that of 

 the travelled granite block; in the neighbourhood of Tromso. In 

 no case doesit exceed the same. Karl Pettersen 



Tromso Museum, Finmarken, Norway 



A NEW FORM OF SPRING FOR ELECTRIC 

 AND OTHER MEASURING INSTRUMENTS* 



IN steam- and gas-engine indicators the pressure of the fluid on 

 a piston produces a slight shortening of a spiral spring which 

 is magnified by a lever, and so the pressure of the steam or gas 

 is recorded. In what are usually known as spring balances 

 there is also occasionally a magnification of the elongation of a 

 spiral spring effected by the use of a rack and pinion. Such 

 magnifying arrangements, however, not only introduce inaccu- 

 racy by the bad fitting of hinges or of teeth, an inaccuracy which 



is aggravated by wear, but they increase the cost of measuring- 

 instruments and their liability to get out of order. 



And, as an example of the difficulty of using the wheel and 

 pinion for the magnification of an angular motion produced by a 

 small force, the authors mentioned the fact that although they 

 used this plan for a year or more in their electric measuring- 



1 Abstract of 'a paper read before the Royal Eocie'V by Profs. W. E. 

 Ayrton, F.R.S., and John Perry.lM.E. 



