23 1 



NA TURE 



[January 6, 1898 



for just below the critical temperature the vertical ingot must 

 behave as a very powerful magnet indeed. 



For all the lesser magnetic fields, there is a temperature of 

 maximum permeability which is nearer to the critical tem- 

 perature the smaller the magnetic field. But at that tempera- 

 ture the magnetic qualities in almost all fields practically vanish. 

 Hence, when the magnetising force is very small, the change 

 from enormously magnetic to almost non-magnetic takes place 

 with extreme suddenness. 



Above the critical temperature, iron is but feebly magnetic ; 

 yet it is still much more readily affected by a magnet than most 

 other feebly magnetic bodies. Not till a white heat is reached, 

 do the magnetic qualities of iron become imperceptible. 



It is not easy in an article like the present to deal with the 

 changes which occur in the electrical resistance of iron, but the 

 following remarks may be of interest : — 



The experiments of Dewar and Fleming have shown that at a 

 temperature of - 200° C. the specific electrical resistance of iron 

 is extremely low. Throughout the range of temperature included 

 between that extreme of cold and the critical temperature, about 

 -f 780° C, the resistance rises at a steadily increasing rate, so 

 that at the latter temperature it is over 150 ti7)ies as great as at 

 the former : far in excess of that of any known alloy at ordinary 

 temperatures (crystalline metals and their alloys excepted), and 

 about equalling liquid mercury for high specific resistance. On 

 still further raising the temperature of the iron, it is found that 

 X^e. rate of rise of resistance, instead of further increasing, very 

 rapidly falls off till, at a white heat, the resistance of iron 

 increases only slowly with the temperature. 



It has long been known that this increasing rate of rise of 

 resistance with temperature is a characteristic possessed by the 

 magnetic metals alone. Here now we see that no sooner does 

 the iron cease to be strongly magnetic than this quality dis- 

 appears, and becomes exchanged for an opposite one, namely, 

 s. decreasing rate of rise of resistance with temperature. In some 

 hitherto unpublished experiments on Hadfield's manganese 

 steel (a non-magnetic steel which can be rendered magnetic by 

 annealing), I have observed a precisely similar change of the 

 resistance-temperature function to take place during the anneal- 

 ing of this steel, thus furnishing a second case of this obscure 

 resistance-change accompanying the change from magnetic to 

 non-magnetic, in one and the same sample. 



The connection between magnetic and electrical properties is 

 evidently not a very simple one, but in the face of these facts it 

 is hard to deny that there is one ; and it is only by trying to find 

 out how the various physical properties depend ujjon magnetism 

 that we may hope to arrive at a comprehensive explanation of 

 that obscure but most-interesting condition of matter. 



David K. Morris. 



EARL V MAN IN SCOTLAND > 



JN Scotland, as in other countries, man existed before the time 

 of written history. The conditions under which his remains 

 are found, and the works which he has left behind him, provide 

 the data for determining their age, not absolutely or capable of 

 being expressed in numbers of years, but relatively to each 

 other. 



Marked differences existed in the physical conditions of Scot- 

 land, and indeed in the northern parts of England also, as com- 

 pared with the southern districts of England and the adjoining 

 parts of France and Belgium at the first appearance of primeval 

 man in those countries. It is the more necessary, therefore, 

 that the conditions then prevailing in Scotland should not be 

 overlooked. 



No evidence sufficient to satisfy geologists has been advanced 

 to prove that man existed in Britain during the period called 

 Tertiary. So far, indeed, as Scotland is concerned, even if it were 

 admitted that in other parts of the globe man had been on the 

 earth during Tertiary times, there is little likelihood that his 

 remains could have been preserved ; for in that country the 

 Tertiary is represented chiefly by volcanic rocks, and a few 

 patches of sand and gravel with rolled sea shells belonging to 

 the closing stages of that period. 



From the careful study which geologists have given to the 

 surface of Scotland, it is evident that at the commencement of 

 the period termed Quaternary or Pleistocene, immediately suc- 



1 A discourse delivered at the Roy<al Institution, London, by Sir William 

 Turner, F.R.S. 



NO. 1 47 1, VOL. 57] 



ceeding the Tertiary, the whole of the country was covered with 

 ice which formed a great sheet 3cxx) or 4000 feet thick in the 

 low grounds, of which the lower boulder clay, or Till, as it is 

 termed, was the ground-moraine. 



As an upper boulder clay also occurs, which is often separated 

 from the lower boulder clay by stratified deposits, some of which 

 contained marine, and others fresh water and terrestrial organic 

 remains, it is obvious that the Ice Age was not one uninter- 

 rupted period of continuous cold.^ The lower and upper tills 

 are the ground-moraines of independent ice sheets, each indi- 

 cating a distinct epoch, separated by an interglacial period. The 

 earlier epoch was that of maximum glaciation, and the ice sheet 

 extended over the north and middle of England, as far south as 

 the Thames Valley and the foot of the Cotswold Hills ; but the 

 high moors in Derbyshire and Yorkshire and the tops of the 

 highest mountains in Wales and Scotland rose above its surface. 

 The great Mer de Glace stretched westward over Ireland into 

 the Atlantic, whilst on the east it was continuous across the 

 North Sea with a similar ice sheet which covered Scandinavia 

 and the region of the Baltic, and extended south to the foot of 

 the hills of central Europe, and overspread much of the great 

 central plain. In the extreme south of England," therefore, the 

 conditions differed from those that obtained in the country 

 further north. Although not actually covered with a sheet of 

 ice, yet the more southern counties had been of necessity under 

 the influence of cold, and must have been subjected to the effects 

 produced by rain and snow, by freezing and thawing. 



During the succeeding interglacial epoch the climate eventually 

 became temperate and genial, and vegetable and animal life 

 abounded. It is to this stage that most of the Pleistocene river 

 alluvia and cave deposits of England and the adjacent parts of 

 the continent are assigned. The British Islands appear at that 

 time to have been joined to the continent, and the same mam- 

 malian fauna then occupied Britain, France and Belgium, which 

 implied similar climatic conditions. As examples of these, it 

 may be sufficient to name the larger mammals, as the cave and 

 grizzly bear, the hyoena, lion, Irish deer, reindeer, hippopotamus, 

 woolly rhinoceros, straight-tusked elephant and mammoth, all 

 of which are now either locally or wholly extinct. 



Abundant evidence exists that man was contemporaneous with 

 these mammals in western Europe, as is shown by the presence 

 of his bones alongside of theirs, and of numerous works of his 

 hands, more especially the implements and tools which he had 

 manufactured and employed. To a large extent these consisted 

 of flint, rudely chipped and fashioned. To these implements, 

 and to the men who made them, the well-known term " Palaeo- 

 lithic" is applied. But along with these, other implements 

 have been discovered, made from the bones, horns and teeth of 

 the larger mammals, on some of which animal forms and inci- 

 dents of the chase have been sculptured both with taste and 

 skill. Up to now, however, no trace of pottery which can 

 without question be referred to Palaiolithic men has been found, 

 and no habitations, except the caves and rock shelters which 

 nature provided for them. 



One may now consider how far northwards in Britain Palaeo- 

 lithic man and the large mammals, with which he was contem- 

 poraneous, have been traced. The exploration of caverns, made 

 by Prof. Boyd Dawkins and other geologists associated with 

 him, has proved that bones of certain of the mammals of this 

 epoch were present in caves in Derbyshire, Yorkshire and North 

 Wales, and that human remains and implements of Paloeolithic 

 type have been found along with them in the Robin Hood cave 

 in the Cresswell Crags, and in caverns in North and South 

 Wales. 



When Scotland is considered, evidence of the existence of the 

 mammals of this epoch is not so abundant, yet the interglacial 

 beds of that country have yielded remains of mammoth, rein- 

 deer, Irish elk, urus, and horse. But notwithstanding the keen 

 scrutiny to which the superficial deposits in Scotland have been 

 subjected by the members of the Geological Survey and others, 

 no traces either of the bones of Pakieolithic man or of the work 

 of his hands have been discovered in North Britain. This, 

 indeed, is not much a matter of surprise, for it must be remem- 

 bered that, subsequent to the genial interglacial epoch, another 

 ice sheet, that of the upper boulder clay, made its appearance, 

 grinding over the surface of the land, wearing away alluvia, and 

 largely obliterating the relics of interglacial times. Hence inter- 



1 For the evidence on which these statements are based, consult the 

 " Great Ice Age," by Prof. James Geikie, edition 1894, also his " Classifica- 

 tion of European Glacial Deposits," in Journal of Geology, vol. iii., April- 

 May 1895. 



