574 



NATURE 



[Oct. 1 6, 1879 



observed even at a temperature of —40° C. The unfrozen 

 fluid is not water, but a concentrated solution of salt 

 thrown out by the freezing of the ice beneath. 



When summer begins, the thawing that occurs is very 

 local and unequal. Any darlc body, such as a heap of 

 ashes or the droppings of bears, eats its way into the 

 snow, absorbing the rays of heat whicli are reflected off 

 again by the general white surface. The bear droppings 

 eat their way into the snow, and then into the ice, 

 and the conical hole thus formed fills itself with water. 

 It may, at last, eat its way right through the ice where 

 not very thick. Thus are formed the greater part of those 

 holes in drift-ice which are usually ascribed to seals. 

 The author never saw a seal's hole in winter. 



A number of interesting experiments were made on ice 

 phenomena. For example, on March 5, a cube of ice 

 was sunk under the ice-field to a depth of five metres. 

 After a lapse of twenty-four hours it was found that a 

 crust of new ice had formed itself over it about i cm. thick. 

 This was caused by the low temperature of the block 

 itself and, from a similar cause, ice-crystals had formed 

 between the edges of the hole, owing to the coldness of 

 its walls. On March 10 very little increase in the 

 added layer of ice on the cube was to be observed. On 

 March 20 this newly-formed ice was found to be softened 

 so that it was easily impressed by the finger ; by April 3 

 it had become harder again, though porous and apparently 

 a little increased. From thence onwards the block 

 dwindled regularly, especially on that part of its surface 

 which was turned upwards ; on July 18 it was only a third 

 of its original size ; nevertheless, the hole through which 

 it was sunk had, during the last period, become entirely 

 closed by young ice at its lower margin. This experiment 

 shows the loss of ice from below by the action of 

 the warmth of the water. The author concludes from 

 his experiments and measurements that compact salt- 

 water ice can never attain a greater thickness than 10 

 metres. 



Icebergs are subjected to disintegration after somewhat 

 the same manner as rocks so commonly are. They are 

 full of crevasses, into which the water formed by melting 

 penetrates ; in winter this water freezes, and by its ex- 

 pansion all through the glacier a rupture of the mass 

 ensues. " It is highly probable that most of the icebergs 

 afloat in winter are in such a condition that a very shght 

 cause is sufficient to make them burst because of their 

 state of internal tension. . . . Every polar traveller can 

 tell how a shot, the driving-in of an ice-anchor, or any 

 other sudden vibration, has brought about the catastrophe ; 

 cases have even occurred in which the sound of the voice 

 alone was sufficient. An iceberg is always an unpleasant 

 neighbour." So many are the causes which tend to destroy 

 icebergs that the author concludes "no berg exists which 

 could withstand them more than ten years, and that 

 commonly the life of a berg is much shorter." However 

 this may be, doubtless the much larger Antarctic bergs 

 last very much longer, as must necessarily occur because 

 of the much greater uniformity of the climate to which 

 they are exposed. 



With regtrdto glaciers, the author quotes an interesting 

 observation of Kane's to the effect that even in lat. 78° 20' 

 during the entire winter, however low be the temperature, 

 the glacier streams never dry up. The melting which 



supplies them with water can only derive its requisite 

 heat from the friction of the ice-masses. 



The chapter on the ice-movements is full of interest. 

 Every field acted on by winds and currents has its own 

 peculiar velocity, depending on the dimensions of the 

 irregularities above and those of the resistances below, in 

 which no two fields are alike. From these differences of 

 velocity arise the irresistible pressures between contiguous 

 fields. The iceberg deeply sunk drifts but slowly, whilst 

 the ice field may travel very fast. If the field catches up 

 a berg in its course, it is broken and torn by the berg ; 

 and as it proceeds on its course its broken fragments are 

 piled up block upon block on the coast of the iceberg. 

 To a casual observer it appears as if the iceberg, driven 

 by a counter current below, were being forced in the 

 opposite direction to the ice-field, so as to plough it up. 

 Many groundless accounts of the existence of such 

 counter currents thus observed have been circulated. 



Another cause of pressure between ice-fields is that, 

 owing to the irregularities on their surfaces, they are 

 twisted round by the action of the wind, which takes 

 hold more on some regions than others. Ever)' field is 

 differently thus acted upon for each direction of the 

 wind. A similar effect is caused by the currents beneath 

 acting upon the irregularities of the under surface. So 

 various are the movements in the ice-fields, that even 

 when the ice lies all the while closed, it is very seldom 

 that any two pieces remain for any length of time 

 in the same position alongside one another. Two 

 ships beset together Isy the ice are' sure sooner or 

 later to be separated. 



The author fully admits that the danger incurred by 

 explorers in the Antarctic regions is very much greater 

 than that to which Arctic voyagers are exposed. The 

 fog in the south is a terrible enemy, and there a ship 

 cannot at once take refuge in the field-ice as in the north. 

 He urges, however, the necessity for^scientific Antarctic 

 exploration and observation, and suggests that a wintering 

 in the lands lying south of Cape Horn could be easily 

 accomplished, and would not require any very extensive 

 appliances. We fully agree as to the benefit to be de- 

 rived by science from a round of meteorological observa- 

 tions and all other kinds of scientific exploration in the 

 Antarctic regions, and heartily wish that such enterprise 

 would take the place of the constant struggles to get to 

 the North Pole. By the mere reaching of the pole there 

 is nothing to be attained. A steamship could very pos- 

 sibly run down from New Zealand direct to Mount 

 Erebus and Terror in a fortnight during the summer 

 months; such an attempt has never been made. It 

 need not be very costly, and possibly the Government of 

 one of the Australian colonies may make it some day. 

 We commend Karl Weyprecht's book to all who study 

 ice phenomena, but not only to specialists, for it is full of 

 interest to all intelligent readers. H. N. Moseley 



THE SILK GOODS OF AMERICA 



The Silk Goods of America. By Wm. C. Wyckoff. 



(New York : Van Nostrand.) 



THIS book has been issued under the auspices of the 

 Silk Association of America, with the view of afibrd- 

 ing information as to the character of the silk goods 

 manufactured in that country. Not many years since 



