May 6, 1920] 



NATURE 



307 



Our Astronomical Column. 



The Lunar Eclipse. — On the whole this eclipse 

 was seen under favourable weather conditions, though 

 for a time there was drifting cloud. The eclipsed 

 portion was easily visible, being at first of a greenish 

 tint, and later assuming the familiar coppery hue. 

 Mr. A, Burnet had prepared a list of stars occulted 

 during totality; they were few, and faint, and only 

 one of these phenomena was observed at Greenwich. 

 There will not be another total lunar eclipse visible 

 in London with the moon at a considerable altitude 

 until November 7, 1938, which is a much longer 

 interval than usual. 



The Nature of Photographic Images. — Dr. Ken- 

 neth Mees, director of the Research Institute of the 

 Eastman Kodak Co., New York, gave an address at 

 the meeting of the British Astronomical Association 

 on April 28 on the nature of photographic images. 

 Various points were raised that are of importance in 

 the application of photography to astrophysics. Thus 

 in the extra-focal determination of stellar magnitudes 

 it was demonstrated that stars of different colours 

 might have their magnitudes arranged in a different 

 order, according to the exposures given and the 

 developer employed. 



Magnified sections of films were thrown on the 

 screen, showing that with some developers the image 

 of a luminous object caused an elevation of the film, but 

 with other developers a depression. In either case the 

 film in the neighbourhood suffers strain (sometimes 

 to the point of cracking), so that images of faint stars 

 near a bright one are subject to displacement. Prof. 

 Turner noted some time ago an apparent displace- 

 ment of a star near a r&seau line which was prob- 

 ably due to this cause. It is possible to minimise the 

 effect by a judicious choice of developer. The address 

 contained many other hints of a practical nature; it 

 will be published in the B.A.A. Journal for April. 

 The Astronomer-Royal, proposing a vote of thanks, 

 said that photography was the only way of obtaining 

 information about the fainter stars in bulk. While 

 some of the phenomena described by the lecturer were 

 a little disquieting, the careful analysis of their origin 

 and effects could not fail to be of great value. 



The Binary Krueger 60.— This system is of par- 

 ticular interest as being one of our nearest neigh- 

 hours, and since the comes has the smallest mass yet 

 found for any star. Astronomical Journal, No. 767, 

 contains researches on the parallax, proper motion, 

 and orbit made at the Leander McCormick Observa- 

 tory by S. A. Mitchell and C. P. Olivier. They find 

 for' the relative parallax 0-266* ±0009". Combining 

 this with the determinations of Barnard, Schlesinger, 

 and Russell, and adding 0005" as the estimated value 

 for the comparison stars, the absolute value 0-261" ± 

 0006" results. 



Their orbit makes the period nearly fifty years, a being 

 2 68", or 10 astronomical units. Hence the combined 

 mass is 0-42 in terms of the sun. The ratio of masses 

 of the two components is still uncertain ; three esti- 

 mates are 0-35, 0-53, and 083. Taking it as 0-5, the 

 faint component is i/7th of the sun in mass, while 

 it is only i/2Sooth of it in luminosity. Prof. Eddington 

 considered that the minimum mass necessary for the 

 attainment of a stellar state may not be much below 

 I /7th of the sun. 



It is pointed out that the photographs of the close 

 pair give as good results as visual measures, while for 

 the distant optical component, observed for the purpose 

 of deducing the relative masses, they are more 

 accurate. Comparisons continued for another twenty- 

 five years should give a satisfactory determination 

 both of the orbit and the mass-ratio. 

 NO. 2636, VOL. 105] 



Leonardo da Vinci.^ 



By Edward McCurdy. 

 A MONG the greater names in the history of Italian 

 -^"^ art some are found to be pivotal by reason of 

 the influence of their work upon that of other artists. 

 Giotto and Masaccio are the most conspicuous 

 instances among the earlier masters. Giotto created 

 the scientific basis of the naturalism of the art of 

 the Renaissance by contrast with the decorative 

 symbolism of the earlier art of Byzantium. Masaccio 

 reinforced these tenets with noteworthy access of 

 realism in the frescoes in the Church of the Carmine 

 in Florence. The names of Antonio Pollaiuolo and 

 Andrea Verrocchio serve to indicate how in Florentine 

 art of the Quattrocento the study of structure gained 

 new scientific precision from anatomical research. 

 Piero de' Franceschi reveals a deeper knowledge of 

 the various problems of perspective, arrangement, and 

 light and shade in his works at Arezzo than was pos- 

 sessed by any of his contemporaries, but the influence 

 which his work would naturally exert was restricted 

 by reason of its remoteness from the greater centres 

 of art training. 



The divergent aims of this small band, who may 

 be termed the upholders of the scientific tradition in 

 Italian art, are realised with singular completeness 

 in the work of Leonardo da Vinci. Born in the year 

 1452, the illegitimate son of a Florentine notary, 

 descended from a long line of Florentine notaries, 

 having shown, according to Vasari, marvellous talent 

 as a boy in the art of design, he was placed by his 

 father in the studio of Andrea Verrocchio, who is 

 described by the same writer as at once goldsmith, 

 master of perspective, sculptor, inlayer of woods, 

 painter, and musician. It was apparently a sort of 

 clearing-house for ideas for the art world of Florence, 

 and there Leonardo became acquainted with Botti- 

 celli and Perugino. His apprenticeship had ceased in 

 1472. for in that year his name occurs in the Red 

 Book of the Guild of Painters of Florence. 



In the vear 1483 Leonardo, being then in his thirty- 

 second year, left Florence and went to Milan, where 

 he entered the service of Ludovic Sforza. Making 

 all possible allowance for what may have been lost, 

 the sum total of his work in art up to this time is 

 astonishingly small as covering the period from his 

 apprenticeship to his thirty-second year. Already in 

 his few pictures the detailed treatment of the herbage, 

 the gradation of the light, the presentment of muscle 

 and tendon, all reveal the scientific study of the laws 

 which, defined their structure. The inference is irre- 

 sistible that while still at Florence he _ had com- 

 menced those studies of natural and applied science 

 the rumour of which, superimposed upon the fame 

 of his artistic work, caused his name to be endowed 

 amons* his contemporaries with a half-legendary uni- 

 versality. Some of the forms of this nascent activity 

 are enumerated by Vasari. I quote from the transla- 

 tion bv Mr. Herbert Home : — 



" In' architecture he made many drawings, both of 

 plans as of other projections of buildings; and he 

 was the first, although a mere youth, that put forward 

 the project of reducint^ the River Arno to a naviffable 

 channel from Pisa to Florence. He made designs^ for 

 flour-mills, fulling-mills, and machines which might 

 be driven bv the force of water. ... 



"And he was for ever making models and designs 

 to enable men to remove mountains with facilitv, and 

 to bore them in order to pass from one level to 

 another; and bv means of levers, and cranes, and 

 screws he showed how great weights could be lifted 

 and drawn ; together with methods of emptying 



1 From a discourse delivered at the Royal Institition on Friday, March 19- 



