ON CATALOGUES OF SPECTRAL RAYS. 53 



direction, swimming with equal ease either backward or forward ; they were 

 never seen to feed, but always appeared to be in search of food, after the manner 

 of the Wrasses, moving slowly round the sides of the pond and rocks, thrust- 

 ing their heads into holes and crevices : when disturbed, they darted through 

 the water with great swiftness. 



The female died on the 6th of July, and on being opened was found to be 

 in very good condition, and to contain a large quantity of ova. 



I have been taking steps to have within the cave behind the pond a case 

 with a glass front so constructed as to enable us to watch the habits of 

 animals with the greatest care. The water in this pond is several degrees 

 lower in temperature than that in the tanks of the Crystal-Palace Aquarium, 

 a circumstance that wUl enable us to study marine life under still more 

 natural conditions. I believe that students of marine life wiU find this pond 

 to be a valuable instrument for the carrying out of prolonged researches 

 in the examination of structure or the development of animals ; and they will 

 find in the keeper an ever willing and obliging assistant and cooperator. 



I cannot close this Report without expressing great regret at the loss 

 of our old friend and fellow naturalist, Jonathan Couch, of Polpcrro. He 

 was a close observer and zealous lover of nature, and only wanted the advan- 

 tages of a less secluded life to have placed him among the foremost of our 

 naturalists. He died at a ripe old age, and, 1 am sorry to say, has left a 

 widow and three children in the greatest straits of poverty, to assist whom 

 would be a kind and generous testimony to a long and well-spent life. 



Preliminary Report of the Committee appointed to construct and print 

 Catalogues of Spectral Rays arranged upon a scale of Wave-numbers* , 

 — the Committee consisting of Dr. Huggins, Mr. Lockyer, Professor 

 Reynolds, Professor Swan, and Mr. Stoney (Reporter). 



The reference of spectral lines to a standard scale of wave-numbers, instead 

 of to a scale of the wave-lengths in air of a given pressure and temperature, 

 or to any of the other scales in use, has very marked advantages. The scale 

 of wave-numbers furnishes to the theoretical inquirer the ratios between wave- 

 lengths, which are what he chiefly wants, in the simplest and most conspi- 

 cuous form, since a series of rays of which the wave-lengths are in geome- 

 trical proportion will be represented by equidistant lines upon the map. No 

 person who has not encountered the task can conceive how tedious it is to 

 carry on a theoretical investigation with any other scale. And to the observer 

 the scale of wave-numbers offers the advantages which have been well stated 

 by Professor C. A. Young in the following words : — " An accurate chart of 

 the solar spectrum on which the lines should be mapped according to ' inverse 

 wave-length,' proposed by Captain Herschel himself, I believe, as well as by 

 Mr. Stoney and others, would sufficiently resemble the spectrum seen in a 

 spectroscope to be equally convenient in the observatory with that of Kireh- 

 hoff, and would be free from the reproach of arbitrariness and irregularity 

 in its sciile. Such a chart would be most gladly welcomed by aUgSpectrosco- 

 pists, and would immediately supersede those of Kirchhoff and Angstrom." 

 (See a letter from Professor Young in ' Nature' of the 6th June, 1872.) 



* The term wave-numbers appears preferable to the equivalent term " inverse wave- 

 lengths " which has been hitherto used. 



