524 Correspondence — Dr. T. G. Bonney Sf Rev. E. Hill. 



of the crystallograpber, to whom the birth and growth of crystals are 

 a study in themselves. Whether we watch with the microscope 

 a tin}' crystal growing from a drop of solution, or contemplate with 

 the imagination the stages by which the fiery lavas of past geological 

 periods sank to rest and crystallised, we view the same process ; 

 it is the transformation of liquid into crystal. Not necessarily into 

 a solid, for recent research shows that there is no dividing-line 

 between liquid and solid ; a plastic solid body may flow ; a solid 

 glass is only a supercooled liquid ; witness, for example, the ex- 

 j)eriments of Adams on rocks and of Tamman on supercooled liquids. 

 The real primary distinction is between crystalline and non-crystalline 

 material, and there is even good reason to believe that some crystals 

 are liquid without ceasing to be crystals. 



The properties of most rocks, of metals, alloys, ice, and many 

 other substances are due to the fact that they consist of crystals, and 

 the importance of the study of the latter is now, I trust, being 

 brought home alike to chemists, physicists, geologists, and engineers 

 in connection with problems relating to the strength, the movements, 

 the origin, and changes of what are usually called solids. 



And so I close, as l)efits a student and teacher of crystallography, 

 with the hope that renewed attention may be paid to this subject, 

 and that it may attract the interest of many a keen intellect in South 

 Africa. The higher scientific studies are now establishing themselves 

 as an integral part of the educational and intellectual life of the 

 country. This is in no small measure due to the South African 

 Association ; and we may hope that the visit of the British Associa- 

 tion will be of some help to her younger sister in the task of diffusing 

 a taste and an interest for the pure truths of science and the studies 

 that they both hold dear. 



GOI^ :E^:Es:F>onsriD.E]isrG:E]. 



THE TRIMINGHAM BLUFFS. 

 Sir, — As no stress was laid on the presence of BeJemnitella 

 miicronata in tlie Chalk at Trimingham, and we do not consider the 

 erratics of that rock in the Cromer district to have made more 

 than short journeys, we cannot agree with Mr. B. B. Woodward 

 about the importance of the literature of the subject since 1883. 

 One of us was acquainted with the general results of Mr. Brydone's 

 work, but thought minute zonal information had no direct bearing on 

 our objections to Mr. Clement Reid's hypothesis. That of a sea-stack, 

 though less open to stricture, involves some serious difficulties 

 which Mr. B. B. Woodward has apparently overlooked. Surely 

 the majority of these masses at Trimingham cannot be ' stacks.' 

 On the right of the reproduced photograph (PI. XXII) boulder-clay 

 can be seen underlying the chalk mass (E) at (F), and another one 

 (C) at (D). Again, if (C) merely rests against (A), to form the 

 roof to the tunnel (B) filled with boulder-clay, it must be an 

 erratic, for sea-stacks are not generally mushroom-shaped. The 

 small chalk mass further east, seen in 1900 (p. 399) but now 

 washed away, must, we think, have been a boulder, while if the 



