NATURE 



[December 5, 1907 



centre of the S is placed over any mark on the horizontal 

 line numbered, say, 9, the point on the periphery of the 

 8 numbered 9 must be superposed on the point on the 

 sinuous curve also numbered 9. 



The description of the sinuous line is a simple case of 

 mechanical drawing, and presents no difficulty. By vary- 

 ing the harmonic composition of the figure of eight and 

 the rate of undisturbed flow of the water, an infinite 

 number of different individual curves can be produced 

 which are all covered by the same generic specification. 

 It is an interesting occupation, in leisure moments, to 

 compose curves of this kind and to compare them with 

 those traced by actual rivers on the face of the earth. 



J. Y. Buchanan. 



It is not difficult to show the character of the flow at 

 the bottom of a small river. For several years I have 

 taken my students along the course of the river Fender 

 near Birkenhead, and we have conducted experiments 

 which confirm the laws of bottom flow first pointed out 

 by Thomson. At first we put down tubes containing 

 coloured liquids, and the stream-line motion was very 

 clearly show^n by lines of colour. Later, I have employed 

 lump sugar soaked in a strong alcoholic solution of 

 magenta. On placing one of these cubes at the outer 

 bend of a curve — the " turnpool "■ — it is found that the 

 water there is almost stagnant. Gradually an aureole 

 of coloured water forms round the sugar as it dissolves, 

 and this slowly creeps across the stream towards the 

 inner bend. The advantage of this method is that the 

 coloured sugar is several minutes in dissolving, and it is 

 very easily carried about. 



For surface flow I have found mahogany sawdust to 

 be the best, as it approaches water in density, and the 

 fine particles are not influenced by air currents. 



.Although in measuring the surface flow the line of 

 maximum velocity is usually more eccentric than the 

 middle line of the stream, there are cases where the 

 quickest flow is near the inner bend. 



In a small experimental river in my laboratory I can 

 produce both effects at will. A river is always tending 

 towards a definite adjustment of its parts to correspond 

 with the characteristics of its flow. The floor becomes 

 graded by the filling of hollows and the removal of 

 obstacles, and the swings become regular and rhythmic 

 lilie the swings of a pendulum. This condition is seldom 

 found except in the flood plains, and I presume this is 

 the special case referred to by Sir Oliver Lodge. 



In the ungraded part many exceptional and interfering 

 circumstances come into play. I have noticed in experi- 

 menting with my laboratory river that when the stream 

 has become perfectly adjusted the line of maximum flow is 

 towards the outer curves, but if any disturbing cause is 

 introduced, such as an increase or decrease in the quantity 

 of water flowing in the channel, a variation in the slope 

 of the bed giving a more rapid or gentler fall, or the 

 introduction of an obstacle to form narrows, the normal 

 characteristics of the flow are disturbed, and the maximum 

 flow may be on the inner curve or more violently bent to 

 the outer curve. This is determined by the changed con- 

 ditions .ind the tendencv of the stream to readjust itself. 

 Prof. Thomson's model, not dealing with graded con- 

 ditions, may easily have produced the abnormal effects he 

 describes. 



A comparison of the flow of a river with that of a 

 glacier shows more points of similarity than most people 

 suppose. In a curved glacier such as the Findelen. the 

 surface at the outer bend is higher than at the inner bend, 

 and the inner bend is always marked by a " toe-cap " 

 moraine like the shallows on the inner curve of a river. 

 It is only reasonable to suppose that this is the result of 

 a cross current under the glacier, such as can be demon- 

 strated in rivers. Moreover, we have in glaciers the 

 phenomena of whirlpools and eddies where tributaries join 

 the main stream. 



The phenomena of flow are practically the same whether 

 the medium is solid, liquid, or gaseous. The essential 

 feature of flow is shearing. In a stream the surface layers 

 shear over the lower, the mid-stream portion shears 



NO. 1988, VOL. yy] 



through the lateral parts, and in a meandering course 

 momentum impels the water towards the outer bends and 

 shears it round the slower moving water in the inner bend. 

 So in glaciers and even in solid rocks flowing under earth 

 stresses the same laws apply. The only difference lies in 

 the unit of shear. In the case of liquids and gases this is 

 extremely small, whereas in glaciers it is usually the 

 " Kugel " which gives rise to the corn structure in glacial 

 ice. In rocks the unit varies from masses of gigantic size 

 to others of very small dimensions. This, perhaps, may 

 be regarded as a very crude conception of the meaning of 

 flow, but I have found it useful in giving students a 

 graphic idea of the complicated movements in rivers and 

 glaciers. J. LoMAS. 



The University, Liverpool. 



Small Flint Implements from Bungay. 



The small flint implements figured in the accompanying 

 drawing were found in a sandy hollow about 2 feet deep 

 at Bungay, in Suffolk. The sand in this hole was littered 

 witli minute flakes ; in a few minutes I picked up between 

 fifty and sixty, of which the figured ones are typical 

 examples. I hesitate to describe the implements as 

 " pigmy flints," because their fine secondary chipping is 

 not confined to the thicker edge or " back " of the flakes, 

 but, judging from photographs I have seen, they closely 

 resemble some pigmies found recently near Brighton by 

 Mr. H. S. Toms. So far as the untrimmed flakes are 

 concerned, it is impossible to distinguish them from typical 



Small flint flakes and implements from Bungay. Two-thirds actual size. 



pigmy flakes, while the trimming of implements 3 and 5 

 is identical with that of the pigmies. 



In consequence of nearly all the English pigmies having 

 been found on the surface of the ground, it has been 

 impossible to say with any confidence whether they belong 

 to the Neolithic, Bronze, or Early Iron period. In view 

 of this, it is interesting to know that the small flakes 

 and implements from Bungay were found in association 

 with a polished axe of grey flint, a black flint lance-head 

 of very delicate workmanship, one of the rare and finely 

 chipped triangular "knives," and some small convex 

 scrapers showing very delicate secondary chipping. These 

 implements were found in the same sandy hole when the 

 small implements were discovered, and from an examin- 

 ation of the sides of the hollow it was evident that they 

 all came from what might be called a " Neolithic floor " 

 about 18 inches from the surface of the ground. Nowhere 

 on the surface of the surrounding ground could I find a 

 single flake or implement, and if the ground had not 

 been disturbed in order that a small quantity of sand 

 might be carted away, not one of the implements would 

 have been brought to light. As it happened, they were 

 all found within an area of about six square yards. Some 



