September 28, 1905] 



NA TURE 



545 



slowly, that in the opaque ones quickly. As this ice thaws 

 in a watch-glass under the polarising microscope, the lumps 

 of quickly frozen white ice exhibit immense numbers of 

 strings — arranged radially alongside one another — of spheres 

 and lenticular masses, ooi mm. to 002 mm. in thick- 

 ness, consisting of very nearly pure water. In each sphere 

 there was a vacuous bubble 00006 mm. in diameter. 



(27) Slowly frozen water showed, on thawing, similar 

 strings of (liquid) spheres and lenticular masses (of larger 

 size, viz. 0-04 mm. to 0-12 mm. diameter), normal to the 

 surface of the block of ice. These spheres and lens-shaped 

 masses had been formed out of solid or hollow cylinders, 

 or long thin cones with local swellings or bulgings. Fre- 

 quently lens-shaped masses bounded by two spherical sur- 

 faces lay in a thin, flat, spiral or warped foam-wall. 



(28) The fibres and cylindrical or conical tubes, like the 

 tubes filled with air, were formed out of thin layers of very 

 viscous, oily liquid, which, as the cooling proceeded, 

 separated out, normal to the surface, and under the in- 

 fluence of the surface tension rolled up, being unable, by 

 reason of excessive viscosity, to form spheres or bubbles. 



(29) When the thawing has gone on for a long time, 

 {ewer foam-walls and larger foam-cells, or glacier grains, 

 appear in the lumps of ice. The strings of liquid spheres, 

 normal to the surface, show an increase in the size of 

 the spheres, caused by the coalescence of the small spheres 

 in the doubly refracting mass of ice into larger ones. An 

 increased amount of salt in the ice assists this coalescence. 

 The tubes or strings of spheres could often be followed 

 continuously through several glacier grains. The partition 

 walls of the glacier grains, when illuminated, often show 

 hundreds of small lens-shaped masses of the same or 

 gradually diminishing size. 



(30) By repeated fractional freezing and melting of the 

 ice crystals formed, continually purer and purer ice is 

 obtained, with increasingly large foam-cells or glacier 

 grains. I have, however, not yet succeeded, even by re- 

 peated slow freezing, in obtaining ice free from foam-walls 

 or from glacier grains. 



(31) .-\ block of transparent ice was cut through, as 

 described by Bottomley, with a loaded wire loop. The 

 loop was of steel wire, or of platinum wire previously 

 heated to redness, and carried 2 kilograms or more. In 

 no case was the plane of section transparent, but always 

 opaque from the presence of solidified foam bubbles of oily 

 salt solution, possessing refracting power, different from 

 that of their surroundings. 



(32) Each separate glacier grain in artificial ice contains 

 a differently orientated crystal of ice, the optic axis of 

 which is very seldom normal to the surface of the ice. 

 When in natural sea ice the optic axes of the separate 

 crystals in the different grains are found to be normal or 

 parallel to the free surface of the water, the separation 

 of orientated crystals of ice may have been started by the 

 contact-action of ice crystals or snow flakes falling on the 

 surface of the super-cooled water, and swimming thereon 

 in a horizontal position. 



(33) The more slowly artificial ice has frozen, and the 

 less salt it contains, the more transparent, rigid, and 

 difficult to cut with a knife it is. 



(34) Every block of artificial ice cleaves, on pressure 

 with a steel point, along the diagonal and median planes, 

 in which, as the ice crystals separated out on freezing, 

 the mother liquor became more concentrated through hold- 

 ing the traces of salt dissolved in a continually diminishing 

 volume of liquid. 



(33) The planes of easiest cleavage in natural ice crystals 

 (laminated structure, displacement without bending) are due 

 to invisible layers of liquid salt solution which are 

 embedded in the crystals, normal to the optic a.xis, or 

 often in other positions. 



(36) Ice crystals at temperatures below 0° consist of 

 doubly refracting viscous liquid, and are intermediate 

 between the soft crystals of serum albumen and ordinary 

 crystals of quartz, felspar, &c. 



(37) At the edge of Tyndall's liquefaction figures, while 

 they are in process of enlarging, or on the bursting of the 

 foam-walls of artificial ice as it melts, one often sees 

 periodic vortex movements. These arise from a periodic 

 capillary spreading out (" .-Vusbreitung ") of the salt solu- 



NO. 1S74, VOL. 72] 



tion of the foam-walls at the boundary between pure water 

 and air or vacuum. 



(38) Tyndall and Huxley observed in white glacier ice 

 transparent lenticular masses bounded by spherical surfaces. 

 These were foam bubbles of water free from air, which 

 were enclosed in a thin skin of oily salt solution and had 

 solidified while embedded in such a skin. 



(39) The blue bands in glacier ice consist of pure ice, 

 while the white bands are composed of ice containing salt 

 and air bubbles. They are formed by the periodical action 

 of solar radiation and by changing pressure, or by the 

 slow descent of the portions rich in salt, or by the slow 

 ascent of air bubbles in the viscous liquid of the glacier 

 ice. 



(40) The ice of the snow flakes which fall on the upper 

 part of the glacier becomes fertilised with inorganic salts 

 derived from disintegrated rocks, and is, as it were, hatched 

 out by the sun's rays, forming " n^vi " or " firn " snow 

 and glacier grains, or foam-cells filled with ice in the 

 glacier proper. The glacier ice travels on, rolling (or 

 " wallowing ") slowly downwards as a living river of ice. 

 Its skeleton of liquid salt solution changes the while, and 

 forms new and larger foam-cells, which, at the lower end 

 of the glacier, perish, disappear, and flow away as the 

 water of the glacier stream. 



THE BRITISH ASSOCIATION. 

 SECTION' L. 



educ.\tional science. 



Opening Address by Sir Rich.^rd C. Jebb, Litt.D., 

 D.C.L., M.P., President of the Section. 



University Education and National Life. 



Every country has educational problems of its own, 

 intimately dependent on its social and economic conditions. 

 The progressive study of education tends, indeed, towards 

 a certain amount of general agreement on principles. But 

 the crucial difficulties in framing and administering 

 educational measures are very largely difficulties of detail ; 

 since an educational system, if it is to be workable, must 

 be more or less accurately adjusted to all the complex 

 circumstances of a given community. .\s one of those who 

 are now visiting South Africa for the first time, I feel 

 that what I bring with me from England is an interest 

 in education, and some acquaintance with certain phases 

 of it in the United Kingdom ; but with regard to the inner 

 nature of the educational questions which are now before 

 this country, I am here to learn from those who can 

 speak with knowledge. In this respect the British 

 Association is doing for me very much what a famous 

 bequest does for those young men whom it sends to 

 Oxford ; I am, in fact, a sort of Rhodes scholar from the 

 other end — not subject, happily, to an age limit — who will 

 find here a delightful and instructive opportunity of en- 

 larging his outlook on the world, and more particularly 

 on the field of education. 



As usage prescribes that the work of this Section, as 

 of others, should be opened by an Address from the Chair, 

 I have ventured to take a subject suggested by one of the 

 most striking phenomena of our time — the growing 

 importance of that part which Universities seem destined 

 to play in the life of nations. 



Among the developments of British intellectual life which 

 marked the Victorian age, none was more remarkable, 

 and none is more important to-day, than the rapid ex- 

 tension of a demand for University education, and the 

 great increase in the number of institutions which supply 

 it. In the year 1832 Oxford and Cambridge were the only 

 Universities south of the Tweed, and their position was 

 then far from satisfactory. Their range of studies was too 

 narrow ; their social operation was too limited. Then, 

 bv successive reforms, the quality of their teaching was 

 improved, and its scope greatly enlarged ; their doors were 

 opened to classes of the community against which they had 

 formerly been closed. But meanwhile the growing desire 

 for higher education — a result of the gradual improvement 

 in elementary and secondary training — was creating new 



