4 6 



NA TURE 



[May 10, 1883 



blacken, new lines appear, and gradually total absorption sets in 

 in the region where the lines are most numerous and close. It 

 is in the range of possibility that the presence of a small quantity 

 of vapour might show itself as a haze over some region of the 

 spectrum ; if, however, the quantity was gradually increased, 

 the haze would give place to lines, and the phenomena just de- 

 scribed would be repeated. Suppose several localities of 

 absorption to exist, the absorptive power of the vapour in- 

 creasing the further down in the infra-red the locality was 

 situated, it might happen that, whilst one locality showed only a 

 haze of absorption, one further down might show total absorp- 

 tion, and some locality between these two should show linear 

 absorption. 



In the case of the absorptions in the solar spectrum we find a 

 very different state of things existing. A comparison of the 

 photographs taken in London on days of different dryness and 

 with those taken at the Riffel, shows that the linear absorptions 

 are not increased in number or intensity ; except so far that the 

 blackness of the lines is increased by the blackness of the banded 

 absorptions, and the same blackness can be induced by placing 

 a certain thickness of water before the slit of the spectroscope : 

 another point is that the Fraunhofer lines in certain regions (-ay 



\ 9420 to A 9S00) are so irregularly distributed as to preclude 

 the idea that they all belong to the absorption of aqueous vapour, 

 yet all are equally darkened by the band, and they do not spread 

 out as the blackness of the band increases. This is against the 

 view of the bands being formed by aqueous vapour, as we 

 know it. 



The question then arises as to what these "water-bands" can 

 be due — if not due to vapour. This we consider an open 

 question, and one which should be discussed. All we can state 

 is that the absorptions shown are similar to those of water 

 (liquid) and they do not seem to point to the watery stuff 

 existing as vapour, 1 if we take the visible spectrum as a guide. 

 An intense blue sky at sea-level is often indicative of moisture 

 in the atmosphere, and it also seems to be indicative of finely 

 suspended matter of some kind. If this be the case, can this 

 suspended matter be suspended water stuff? for if it be not, 

 there is no reason why the sky should be bluer on a nn .i-t day 

 than on a dry day. We would remark that the deep blue sky 

 at sea-level is of a different colour to the black-blue of high 

 altitudes where, if they exist, the fine suspended particles would 

 be largely diminished in number, and the coarser particles which 

 cause white haze would also be few er. The great difference of 



7000 



Fig. I. 



Fig. 2. 



Fig. 3. 



Fig. 4. 



Fig. 5. 



Fig. 6. 



10,000 



the intensities of the light from the blue sky in England and at 

 10,000 feet was determined by one of us and communicated to 

 the British Association at Southampton, and the enormous dis- 

 parity between the two has some bearing on the question we 

 have been discussing. 



In the above paper we have described the absorption due to 

 "water stuff" in the atmosphere to A. 9800, as it is only to that 

 wave length to which the normal spectrum has been as yet 

 published. We wish however to add that there are bands in 

 the solarspectrum commencing at 1 A9S00, A. 12,200, and A. 15,200, 

 and giving step by step absorptions from one wave-length to the 

 next, as in the diagram, which also corresponds with cold water 

 bands. The absorption in the locality from 12,200 downwards 

 is usually total, and it is only on dry cold days or at high alti- 

 tudes that rays of sufficient amplitude can penetrate to cause 

 photographic impression to be made. 



April 5. — "Observations on the Colouring-matters of the 

 so-called Bile of Invertebrates, on those of the Bile of 



1 These wave-lengths are taken from the map from the Phil. Trans., 

 1880, and are only to be considered approximate. 



Vertebrates, and on some unusual Urine Pigments, &c. ," 

 by Charles A. MacMunn, B.A., M.D. Communicated by Dr. 

 M. Foster, Sec.R.S. 



In this paper the result of a systematic examination of the bile 

 and various extracts of the so-called liver of Molluscs and Arthro- 

 poda, and of the pyloric or radial cceca and other appendages 

 of the digestive system of Echinodermata is described. The 

 universal distribution of one colouring-matter, which by appro- 

 priate experiments is shown to be a chlorophyll pigment, is 

 proved. It occurs in the above organs, and can be detected in 

 the bile of specimens of Helix after a six months' fast ; for this 

 colouring-matter, since it is found in the appendages of the 

 enteron, the name enterochlorophyll is proposed. The slight 

 differences observable in different cases are shown to be due to 

 the probable greater or less amount of the usual chlorophyll con- 

 stituents, blue chlorophyll, yellow chlorophyll, and chlorofucine, 

 and the presence of xanthophyll, lutein, or tetronerythrin. Entero- 

 chlorophyll is shown to be much more abundant in the liver of 

 Mollusca and in Echinodermata than in Crustacea, as the livers 



1 Unless it be held that the water itself holds vapour involution. 



