Part 3

I remember, when I first began to be interested in crystals in undergraduate days, reading in _Nature_ an account of two papers which seemed to have a possible bearing on the subject. One is an example of a stationary arrangement of rigid bodies. The other illustrates the principle which I am now suggesting, and is an arrangement of pulsating bodies whose positions are due to their movements. The first was a description of MAYER’S experiment on floating magnets which was, if I remember right, shown here in a BOYLE Lecture by Sir JOSEPH THOMSON a few years ago; an experiment in which magnets suspended in water by corks and with their North poles projecting so that they repel one another, are brought together by the attraction of a large magnet held, with its South pole downwards, above the surface of the water; under the joint influence of this attraction and their own mutual repulsions, they group themselves into a number of interesting geometrical figures very suggestive of the geometrical regularity of crystal structure. Indeed, attempts have been made by LEHMANN to explain the architecture of a crystal by a grouping of magnetic systems. And the other was the experiment of BJERKNES in 1876 (described in _Nature_ in 1881), in which a number of hollow elastic balls were made to expand and contract by means of air tubes attached to them. These pulsating balls, when placed in water, attracted and repelled one another like magnets, and arranged themselves in a regular manner; thus suggesting that there may be many unexpected ways in which rhythmical motion can exercise an attractive and directive action such as is required to produce a crystal.

Let me illustrate what I mean by another crude analogy. Take a room full of dancers; if they are all dancing to different times and in different ways there will be no order or arrangement in the crowd, and it will remain an incoherent jostling assembly of independent persons. But if there are among them those who are moving to the same step and in the same manner, and if they come together, they can become partners and can continue to dance together; and if the room be filled with such dancers, then the whole assembly can grow together into an orderly movement, and only those whose step does not fit into the dance will be ejected and left out. Or take another example: soldiers marching together have not ceased to be individual men, but when they fell into step they became in addition an organized body with a structure and a coherence that does not belong to a miscellaneous crowd. Even so may the particles of dissolved salt be endowed with a movement which enables them to enter into partnership and cohere, and so to build themselves into the orderly structure which makes up a crystal. And even so do crystals grow out of a mixed solution as a pure and homogeneous substance and reject the other materials which are dissolved in the liquid.

One other suggestion. If the growth of a crystal is really the coming together of vibrating particles which cohere because they are in tune with one another and so enter into a partnership like that of the dancers or the figure skaters, then is it not possible that we may be able to communicate these vibrations to a supersaturated solution, which is so densely crowded that it is ready to crystallize, by some other means than by inoculating it with the appropriate crystal? I think that the time has come when we may be able to get some knowledge of the manner of these movements by experimental methods; perhaps by studying the sort of shock or movement, if there be any such, which starts crystallization in a supersaturated solution; perhaps by finding other substances, whose movements we understand, which are able to start the crystallization when they are introduced into certain solutions.

I have said that the frontier problems in science are interesting; and that this is true not only of the events that take place when different bodies meet, but in another and more general sense. The most interesting and fruitful problems are those which deal with the borderland between two sciences, when the difficulties of the one are enlightened by the experience of the other, or when the same problem is looked at from two different sides. Let me only quote as an illustration the work connected with osmosis, which attracted first the botanists and then the physical chemists, and remind you of the enormous importance which it has assumed by their combined efforts. I think it will be found that these problems of crystal growth are of this borderland nature. And such problems can only be satisfactorily attacked by those who are more than mere specialists and can be led by the experience or the analogies of other sciences.

I said that I should like to regard this lecture as an attempt to justify the value of analogy. We poor specialists grope within the confines of our own science, and what little advance we make is made in part by the light we borrow from the other sciences. In these days of increasing specialization what we need is to interest in our own problems, not only those who are tilling the same fields with ourselves, but even more, those who live on the other side of the fence which surrounds us: to call to them across the frontier, to seek their advice and assistance and the benefit of their experience.

This is one of the great advantages of a University, that workers and thinkers in different subjects are brought together and can make their difficulties known to each other. The connecting links between them are the analogies which they perceive and which excite an interest that they would not otherwise feel in each other’s work.

This is the reason why I have endeavoured to set before you a very special problem in a very elementary way and as far as possible without using technical terms. It is with the hope of attracting the interest of workers in other subjects to this fascinating problem of crystal growth which, from the time of BOYLE to that of RUSKIN, and more especially, as I have shown you, in recent years, has engaged the attention of Oxford students of crystals.

Transcriber’s note:

Page 8, ‘allum’ changed to ‘alum,’ “corpuscles of nitre, alum, vitriol,”

End of Project Gutenberg's The Growth of a Crystal, by Henry A. Miers