2.^2 



NA TURE 



[January 7, 1892 



to be photographed can be observed just before exposure, 

 which insures the centrality of its image on the sensitive 

 film. 



The extension of this branch of chronophotography, if 

 taken up and developed, may be of great use to medical 

 science, for many occurrences, happen where such an 

 apparatus as the above would be invaluable. One of 

 the examples done by this method is shown in Fig. lo, 



while on its upward bound the decrease is also apparent, 

 perhaps not so much, on account of the ball approaching 

 the camera. 



Although we have not quite touched on all the subjects 

 referred to in the very interesting article by Prof. Marey, 

 yet we trust we have given the reader an idea of what 

 kind of work has been going on in this direction, and 

 the methods that have been adopted to produce such 



Fig. 10. —Showing the movements of Vorticella:. The phases of movements must be read from left to right. 



and illustrates the movements of Vorticellte, which refract 

 their stalks in spiral fashion. Many other proposals, 

 not yet carried out, are mentioned by Prof. Marey, and 

 include the production of photographs showing the move- 

 ments of blood corpuscles in the capillary tubes, the 

 intimate actions of the contraction of the fibre of the 

 muscles, and the waves which pervade them 



Prof. Marey also applies chronophotography to move- 



good results. The branch that we look .forward to being 

 greatly extended is that in which the microscope takes 

 the prominent part. W. 



Fig. II. — Series of positions taken up by a falling ball studied by chrono- 

 ph (tC'graphy on a fixed plale. 



ments of objects in physical as well as in biological 

 science, but although several cases are mentioned, we 

 will only refer here lo the instance he gives of the falling 

 ball (Fig. 1 1). 



The intervals between each image of the ball, although 

 different in space, are equal in time, and the illustration 

 brings out clearly the gradual increase of the velocity ; 



NO. I 158, VOL. 45] 



SIR GEORGE BIDDELL AIRY. 



A17E greatly regret to have to record the death of Sir 

 * * George Biddell Airy, whose name has been familiar 

 to the scientific students of more than one generation. He 

 died on Saturday evening last, in his ninety-first year. In 

 the summer he received by a fall an injury which rendered 

 a surgical operation necessary. Although at the time this 

 seemed to be successful, he never really recovered from 

 the shock to his system. 



On October 31, 1878 (vol. xviii. p. 689), we published 

 a portrait of Sir George Airy in our series of " Scientific 

 Worthies," and at the same time we gave a full account 

 of his work as a man of science. We need not now, 

 therefore, do more than note the main facts of his career. 



He was born at Alnwick, Northumberland, on July 27, 

 1801, and received his early education at private schools 

 in Hereford and Colchester, and at the Manchester 

 Grammar School. In 1819 he entered Trinity College, 

 Cambridge, as sizar. Here he soon gave proof of a 

 remarkable aptitude for mathematics, and in 1823 he 

 graduated as Senior Wrangler. In the following year he 

 was elected a Fellow of his College, and in 1826 he became 

 Lucasian Professor of Mathematics. He was full of en- 

 thusiasm for experimental science and applied mathe- 

 matics, and in 1824-25 had published papers on "The 

 Lunar and Planetary Theories," on " The Figure of the 

 Earth," on "The Undulatory Theory of Optics," on 

 " The Forms of the Teeth of Wheels," and on " Escape- 

 ments." After his appointment to the Lucasian Pro- 

 fessorship, he continued to make important contributions 

 to the knowledge of such subjects, devoting himself with 

 especial ardour to the study of undulatory optics, which 

 was at that time a new field of research. 



He was elected Plumian Professor of Astronomy in 

 1828, a position with which was associated the director- 

 ship of the Astronomical Observatory. Here he 

 superintended the erection of several instruments, and — 

 in accordance with the example set by Maskelyne, 

 and followed by Bessel and Struve — introduced a 

 thoroughly efficient system for reducing the observations, 

 which were printed annually. He also carried on theo- 

 retical studies. In 1831 he published in the Transactions 



