1869.] The Future Water-supply of London. 225 



temporary phenomena are of frequent occurrence, in which some of 

 these minute pores are enormously increased in size, and become 

 " spots." The inner portion of these spots is not uniformly dark, 

 but contains usually a still darker spot. The writer in one instance 

 found that the light of the inner j)art of a spot was about three 

 times that of the light of the atmosphere near the sun's limb. 

 "When the light of the umbra is examined in the spectroscope the 

 lines of Fraunhofer are found increased m width in a small degree, 

 as is shown in the Plate, Fig. 3. Mr. Lockyer made independ- 

 ently a similar observation. In April, 1868, the writer found in 

 the spectrum of a spot that the lines C and F were not widened. 

 This observation is of some interest, now that we know that two of 

 the three bright lines of the prominences are coincident with the 

 dark lines C and F. 



The writer prefers not to build any speculations on these facts 

 at present, since, in his opinion, the precise state of things which 

 constitutes a sun-spot is not certainly known. The fragmentary 

 character of the latter portion of the article has been owing to the 

 writer's desire, not to omit some recent observations in this won- 

 derful method of analysis, which promises to aid us in the solution 

 of numerous cosmical problems hitherto deemed inscrutable, and 

 greatly to extend our knowledge of the universe. 



VI. THE FUTUEE WATER-SUPPLY OF LONDON. 



By C. W. Heaton, F.C.S., Professor of Chemistry in the Medical 

 School of Charing Cross Hospital. 



The long-expected Report of the Royal Commission on Water-supply 

 will, it is to be hoped, be presented to Parliament in the course of 

 the present session. Its pubhcation will probably put us in pos- 

 session of the most important document ever issued on this most 

 important subject ; for it is understood to contain many new and 

 some rather starthng results, in addition to the complete epitome of 

 previously acquired knowledge, which was to be expected from the 

 high reputation of its authors. In the meantime the public slumbers, 

 as it generally does in England in the intervals of the periodical fits 

 of energy in which so much of the real work of reform is done. To 

 one whose study has brought him face to face with any of the great 

 problems of sanitary reform, it is, indeed, a never-ceasing wonder 

 that slumber, in the presence of such fearful questions, should at any 

 time be possible ; and he is apt to feel thankful to any monitor — even 

 to the death-dealing cholera — that succeeds in awakening men to 

 life and work. It is marvellous, certainly, that so enlightened, 



