NA TURE 



297 



THURSDAY, JUNE 8, 1916. 



THE MOVING PICTURE AND ITS 

 MECHANISM. 



Hopwood's Living Pictures : Their History, Photo- 

 Production, and Practical Working. By R, B. 

 Foster. New edition, revised and enlarged. 

 Pp. x + 377. (London : The Hatton Press, Ltd., 

 191 5.) Price 65. net. 



THE last twenty years have seen such amazing- 

 development, both technically and indus- 

 trially, in all that pertains to moving-picture de- 

 vices that it is difficult to realise how long ago 

 observations were made and simple devices con- 

 structed which by slow degrees led to the position 

 from which the present activity has sprung. The 

 whole story is well told in the new edition of 

 Hopwood's "Living Pictures." The reviser has 

 the advantage not only of a good scientific edu- 

 cation, but also of that special training required 

 for members of the legal profession, and this is 

 reflected throughout the book in the strictly 

 accurate statements of the problems at every stage 

 and lucid descriptions of the method of solution. 

 Further, the classification of the numerous modes 

 adopted by different inventors for arriving at the 

 desired end is a help to the reader and avoids the 

 confusion which a merely chronological treatment, 

 for instance, would introduce. Two other features 

 should be mentioned. The early history, begin- 

 ning with the observation of Dr. Roget on the 

 appearance of the spokes of a wheel seen through 

 a fence, is interesting, in that we find how many of 

 the best-known scientific workers made contribu- 

 tions to the general subject. The following is a 

 list of some of these : Brewster, Wollaston, 

 Babbage, Herschel, Plateau, Faraday, Savart, 

 W'heatstone, Clerk Maxwell, Marey, Janssen. 



The second feature for which we have to thank 

 the reviser is the excellent account of the legal 

 side of the question, not only with regard to the 

 restrictions where public exhibitions are con- 

 cerned, but also in respect of the patents bearing 

 on the subject, of which there is a complete classi- 

 fied list. Unfortunately, owing to considerations 

 of space, this only contains the date and number, 

 but not the name of the patentee or the title. In 

 addition there is a valuable exposition of the state 

 of the law in relation to copyright. It appears 

 to the writer that the inventor will find this book 

 of great use, owing largely to the careful way 

 in which the problems are dissected and classified 

 under sub-subjects, so that whatever ideas he may 

 have he will be able to compare with existing 

 practice or proposals by reference to only a few 

 pages. 



The subject is so vast that it is impossible in 

 a notice to discuss more than one or two parts 

 of it. The author has, in the historical section, 

 preserved an astonishing number of inventors' 

 names for their instruments, derived mostly from 

 the Greek. The greater number of these are now 

 wholly forgotten, though Thaumatrope, Zoetrope, 



NO. 2432, VOL. 97] 



and several others are still remembered. Later 

 inventors, with their kinematographs vulgarised 

 to sinnema and other -graphs and -scoi)es, have, 

 however, not entirely succeeded in imposing this 

 class of language upon the profession, who have 

 adopted the short and simple expression " movies " 

 as a general term for moving pictures. 



In the earlier discussions it is natural that the 

 question of p>ersistence of vision should have 

 claimed much attention. The accepted views have 

 been revised from time to time when new demands 

 were made upon this physiological limitation, 

 as, for example, when three-colour moving pic- 

 tures or stereoscopic moving pictures, in which 

 the two eyes alternately see succeeding views, 

 were first discussed. It is a question whether per- 

 sistence of vision is an accurate expression in rela- 

 tion to moving pictures at all. It is exact where 

 the eye blends a number of successive views 

 of a stationary object, but where the successive 

 views are obtained of a moving object persistence 

 is exactly what is not present. That which the 

 brain creates for the eye is a supposed seeing of 

 the object in all the intermediate positions which it 

 never really sees at all, giving the idea of equable 

 movement. Those who are familiar with the old 

 slipping magic-lantern slides, or remember the old 

 Zoetrope slides, will realise how much the brain or 

 the imagination can do in this respect. The 

 modern moving picture does not call for a fraction 

 of this creative faculty, except that projected pic- 

 tures, as distinct from illuminated pictures, seem 

 to make much greater demands upon it. It is 

 probable that the reason for this is that the really 

 successful Zoetrope slides were those in which the 

 prominent feature was a large object moving 

 slowly, and, perhaps, turning also, while those 

 with many small moving parts were not a success. 

 The modern moving picture must of necessity meet 

 all cases as they arise, but, even so, there remains 

 obvious the greater perfection of the view presented 

 by large objects moving slowly, as, for instance, 

 wave motion on water, as compared with smaller 

 objects in quicker movement, such as the arms and 

 legs of living creatures, while the spokes of a 

 moving wheel which succeed one another about as 

 often as the individual pictures in the series do 

 remain hopelessly unmanageable. 



Chap, iv., on "Film Machines and Intermit- 

 tence ^Iechanisms," is one of special interest, and 

 it well illustrates the excellence of the classifica- 

 tion, for every known method of arresting the film 

 for the necessary time, or of making it appear 

 stationary- by optical means, even though it is in 

 reality moving continuously, is set out under a 

 suitable heading, and the mechanical diflficulties 

 and limitations of the different methods are well 

 explained. In the writer's opinion, the discussion 

 of the Maltese Cross movement, a movement of 

 the type of the Geneva stop mechanism of clocks 

 and watches, is treated in an unnecessarily cum- 

 brous manner. This is due to the use of trigono- 

 metrical expressions, - which are not well 

 adapted for the treatment of this class of move- 

 ment. Some seven pages might be replaced by 



