i86 



■NA TURE 



[February 26, iqo^ 



advisabilily of endeavouring to go so far. We are as 

 yet far too ignorant of the nature of the relations existing 

 between cytoplasm and nucleus to be able to draw any 

 safe general conclusions respecting them. What we do 

 know suffices to prove that, probably as the result of 

 interchange of material, the relations are at least of a 

 very intimate nature. 



It is, of course, impossible within the limits of so short 

 a notice to attempt to do anything like full justice to the 

 skilful treatment that Prof. Verworn has brought to 

 bear on his subject. It must suffice to repeat that it is 

 thoroughly well worth reading, and whatever may be 

 thought of the tenability of the hypothesis itself, one 

 ran hardly deny that it does fulfil the important condition 

 of enabling one to link together in a suggestive manner 

 a large number of very complicated phenomena. 



SCIENCE AND PRACTICE. 

 The Lighthouse Work of Sir James Chance, Bart. 

 Pp. x + 162. (London : Smith, Elder and Co., 

 1902.) Price 5s. net. 



THE optics of lighthouse lenses form a sufficiently 

 fascinating subject, and its interest, apart from 

 its practical importance, has attracted able men from 

 Augus::n Fresnel down to John Hopkinson. Among 

 these, James Timmims Chance deservedly holds a 

 prominent place, and his biographer has earned our 

 thanks by the account he has given in the pages 

 under notice of Chance's life and work. 



Sir James Chance, a son of Mr. William Chance, of 

 Birmingham, one of the partners in the glass-making 

 firm of Chance Bros, and Co., was born in 1814. 

 After gaining honours in various subjects, including 

 Hebrew, at University College, London, he entered 

 Trinity College, Cambridge, and in 183S he 

 graduated as seventh wrangler. Immediately after 

 this he entered his father's firm, of which he re- 

 mained a partner for fifty years, being head of the 

 firm for twenty-five. He was made a baronet by her 

 late Majesty on the occasion of her last distribution 

 of birthday honours. He died on January 6, 1902. 



In old days, parabolic reflectors were used for light- 

 houses; the employment of lenses is due to Augustin 

 Fresnel, who in 1819 erected the first dioptric system 

 at the Tour de Cordouan ; the system was extended 

 by his brother Leonor and other distinguished men 

 in France, and in Great Britain by the family of 

 Stevenson, by Airy and by Faraday. With the two latter 

 Mr. Chance became intimately associated about the 

 year 1859. 



His firm had manufactured lighthouse lenses for 

 Mime years previously. Before this, the industry had 

 b :en crushed out in England by Excise regulations ; an 

 Order in Council was required to permit of their manu- 

 facture, and a duty amounting to some 300 per cent, 

 on the cost of the glass was enforced. In conse- 

 quence, Messrs. Swinburne and Co., of South Shields, 

 who for a few years had manufactured lenses, gave 

 up the work in 1845. In 1850 Messrs. Chance took it 

 up. They engaged a French expert, M. Tabouret, 

 who had worked for Fresnel himself, and he exhibited 

 in the Exhibition of 1851 an apparatus of the first 

 NO. 1739, VOL. 67] 



order, made at Messrs. Chance's Spon Lane works. 

 In the years that followed, the work prospered, the 

 plant was increased and the optical part of a number 

 of lighthouses was manufactured. M. Tabouret left 

 the firm in 1853. 



In 1859 the work of the Commission to inquire 

 into the condition of the lights, buoys and beacons of 

 the United Kingdom began. Airy and Faraday had 

 charge of the scientific side of the inquiry. Mr. 

 Chance's assistance was called in as a manufacturer 

 of great experience, and it was soon found that in 

 him the Commission had an adviser who could render 

 services of the highest value. His mathematical 

 training enabled him to understand and develop the 

 theory of the subject, his practical experience showed 

 him what was possible. He had already introduced 

 improvements into the method of grinding the an- 

 nular lenses which form the system, and its various 

 components had reached a high degree of perfection. 



But, though this was so, the distribution of light 

 effected by means of the lens system was, in many 

 cases, entirely wrong. At that time Messrs. Chance 

 were not allowed even to tender for the frames to 

 hold the lenses, although they had to make these 

 in order to adjust the system in their workshop. 

 They had no share in the erection or adjustment of 

 the light, which was done usually by contractors with 

 little or no optical knowledge, and the result was 

 failure. One of the most glaring instances was the 

 Whitby light, of which Airy reported : — " The 

 dioptric part of the apparatus is beautiful. The glass 

 is of the best quality. ..." The adjustments, 

 however, were all wrong. 



" My impression is," he writes, " that in the north 

 lighthouse three-fourths of the light is absolutely 

 thrown away, and in the south lighthouse nine-tenths 

 of the light is absolutely thrown away. . . . When 

 with a ruler I covered the part of the flame which 

 merely gave light to the sky, it was absurd to see 

 how little was left for the useful part. ... It 

 really gave me a feeling of melancholy to see the 

 results of such exquisite workmanship entirely 

 annihilated by subsequent faults in the mounting and 

 adjustment." 



In the end, Mr. Chance was given a free hand. 

 Airy again reports, at a later date, 



" The «aid constructor " — Mr. Chance — " is willing 

 to go heartily into the improvement of the Whitbv 

 light, therefore leave all others and rest on it." 



And this wise advice was taken. 



A method of adjustment — it seems sufficiently 

 obvious, and had been used previously — was sug- 

 gested by Airy and employed in setting up the lenses. 

 Each portion of the lens system is to be emplo) d 

 in forming an image of some part of the lamp flame 

 on the distant horizon or on some part of the sea be- 

 tween the lighthouse and the horizon. Conversely, if 

 the adjustment is correct, a real image of that part of 

 the horizon will be formed by the lens system on the 

 corresponding part of the flame, and can be seen by 

 an observer looking into the lens system from behind. 



Airy's method consisted in adjusting the lenses in 

 turn until the image of the horizon formed by each 

 occupied its proper position with regard to the flame. 



