NATURE 



145 



THURSDAY, JUNE 16, \\ 



ON LABORATORY ARTS. 

 On Laboratory Arts. By Richard Threlfall, M.A., 

 Professor of Physics in the University of Sydney. Pp. 

 xii + 338. (London : Macmillan and Co., Ltd. New 

 York : The Macmillan Company, 1898.) 



THERE are certain passages in the preface of Prof. 

 Threlfall's valuable contribution which it may be 

 useful to quote before dealing with the book itself. 



" It often happens that young physicists are to be 

 found whose mathematical attainments are adequate, 

 whose observational powers are perfectly trained, and 

 whose general capacity is unquestioned, but who are 

 quite unable to design or construct the simplest apparatus 

 with due regard to the facility with which it ought to be 

 constructed. That ultimate knowledge of materials and 

 of processes which by long experience becomes intuitive 

 in the mind of a great inventor of course cannot be 

 acquired from books or from any set course of instruc- 

 tion. There are, however, many steps between absolute 

 ignorance and consummate knowledge of the mechanical 

 arts, and it is the object of the following pages to assist 

 the young physicist in making his first steps towards 

 acquiring a working knowledge of ' laboratory art.' . . . 

 Before all things the means indicated must be definite 

 and reliable. It is for this reason that the writer has 

 practically confined himself to matters lying within his 

 own immediate experience, and has never recommended 

 any process (with one or two minor exceptions, which he 

 has noted) which he himself has not actually and person- 

 allycarriedthroughto a successful issue. . . . Withregard 

 to the question as to what matters might be included and 

 what omitted, the general rule has been to include in- 

 formation which the author has obtained with difficulty, 

 and to leave on one side that which he has more easily 

 attained. . . . Though no doubt a great deal can be 

 <lone with inferior appliances where great economy of 

 money and none of time is an object, the writer has long 

 felt very strongly that English physical laboratory prac- 

 tice has gone too far in the direction of starving the 

 v.orkshop, and he does not wish, even indirectly, to give 

 any countenance to such a mistaken policy." 



The writer of this notice feels so strongly the im- 

 portance of the subject of the first and last of these 

 extracts that it is only with an effort that he can forego the 

 opportunity which they offer of airing views, and confine 

 himself to the more prosaic duty of review. 



The second extract is one which shows that the first 

 essential in a work of this kind is complied with. A 

 mere collection of recipes for making and doing all sorts 

 of things which have been collected from anywhere and 

 everywhere, while not absolutely useless, is necessarily 

 intrustworthy. Without the personal certificate of a 

 lan who is both a physicist and a mechanician, no de- 



ription of a process for making or doing anything will 

 necessarily be the most appropriate or even serviceable 

 at all. With such a certificate, however, any one with 

 but little experience of any particular laboratory art may 

 set to work upon it with reasonable confidence. 



The first chapter, of ninety pages, is upon the manipu- 

 lation of glass and on glass-blowing for laboratory pur- 

 poses. Of all laboratory arts probably glass-blowing 

 and working, not including the work of the optician, 

 looks more easy when practised by an adept, and seems 

 NO. 1494, VOL. 58] 



more utterly and hopelessly impossible when tried for 

 the first time, than any other. It is one which every 

 experimentalist must acquire in some degree, and which 

 as a fact, with a little practice and suitable help, is one 

 of the easiest in which to make progress. Shenstone's 

 well-known little book has been found invaluable by 

 many, the little work of Bolas has recently been reviewed 

 in these columns, and now we have new advice on the 

 same subject, differing in some points, as is to be ex- 

 pected, but the result of personal experience. The 

 subject is one in which any opportunity of watchmg 

 a glass-blower of skill is worth more than any written 

 instruction, but it is one in which occasional and hurried 

 opportunities of watching a process can be supplemented 

 most usefully by description. Practice, however, is 

 essential, whatever guide to procedure maybe attainable. 



The writer's experience of the average student is that 

 it is not sufficient to tell him even several times that he 

 must not begin glass-blowing operations upon dusty 

 tubes. The very elaborate description of a really proper 

 way of cleaning a glass tube so as to fit it for the best 

 class of work may, perhaps, induce this individual to 

 take the trouble at least to wash out his tubes. 



Prof. Threlfall does not approve of the type of blow- 

 pipe usually furnished by the instrument maker, nor 

 apparently does any writer on the subject. He describes 

 a simple form of oxygen blowpipe that is suitable for 

 working lead-glass or unusually infusible glass. For 

 larger work with lead-glass he prefers a system of four 

 blowpipes, the flames of which meet upon the work. 

 The superiority of lead-glass where the nature of the 

 experiment will admit of it is duly insisted on. It is a 

 pity that owing to the miserable blowpipes to be found 

 in laboratories, the beginner never gets a chance of 

 realising how excellent lead-glass really is. 



The instructions given for cracking or cutting the 

 larger sizes of glass tubes do not quite accord with the 

 writer's experience. The well-known point of melted glass 

 and the flame-pencil with a very small flame are described 

 as being suitable for leading a crack round a tube. The 

 writer has found with tubes that are not too large, a 

 thick copper wire mounted in a handle and bent at the 

 end into such a form as to make a good long contact 

 with the glass, enables one with a little practice to lead a 

 smooth crack round the tube along any predetermined 

 line with an accuracy and quickness not approached by 

 any other process. It is often possible with a single 

 heating of the wire to " cut " a tube an inch or more in 

 diameter either square across or at an angle as great as 

 30°, and so nearly in a plane that five minutes' grinding 

 on emery cloth will remove the whole of the old surface. 



On p. 49 there is a figure showing an ordinary glazier's 

 diamond mounted on a frame, so as to bear upon the 

 exterior of a rotating tube. No doubt as this is described 

 a tube may be cut that way, and in that case, perhaps, 

 no exception should be taken. But since glass tubes 

 cool from the exterior, the inner surface is ultimately in 

 a state of stretch, while the exterior surface is in a state 

 of compression, hs a consequence, glass tubes and 

 vessels in general are far more sensitive to even micro- 

 scopic scratches inside than out. For this reason, it is 

 preferable to mount the diamond at the side of the end 

 of a stick or metal rod provided with a sliding stock 



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