Sept. 18, 1884] 



NA TURE 



501 



of the sections passed through by a very large number of wells 

 and borings ; a daily record has been obtained of the height at 

 which water stands in many of these wells ; investigations have 

 been carried out as to the quantity of water held by a cubic foot 

 of various rocks, by Mr. Wethered ; and as to the filtering power 

 of sandstones, and the influence of barometric pressure and lunar 

 changes on the height of underground waters, by Mr. I. Roberts. 

 During the present year the attention of the Committee has been 

 directed to the remarkable influence of the earthquake which 

 visited the East and East-Central Counties of England in March 

 last, in raising the levels of the water in the wells of Colchester 

 and elsewhere. More detailed information is still required as to 

 the proportion of actual rainfall absorbed by various soils, over 

 extended periods representing typical dry and wet years. In- 

 formation on these heads and on other points of general interest 

 bearing on the percolation of underground waters, referring to 

 observations made in Canada or the United States, would be 

 gladly welcomed by the Committee, and would be incorporated 

 in their eleventh and final Report to be presented next year. 

 Your Committee seek reappointment, but do not require a grant, 

 as they have forms of inquiry on hand, and did not require to 

 expend the whole of the grant of last year, a portion of which 

 only has been drawn. 



Appen lix — Copy of Questions. — I. Position of well or shafts 

 with which you are acquainted, la. State date at which the 

 well or shaft was originally sunk. Has it been deepened since 

 by sinking or boring ? and when ? 2. Approximate height of 

 the surface of the ground above Ordnance Datum (mean sea- 

 level). 3. Depth from the surface to bottom of shaft or well, 

 with diameter. Depth from surface to bottom of bore-hole, 

 with diameter. 3a. Depth from the surface to the horizontal 

 drift-ways, if any. What is their length and number? 4. Height 

 below the surface at which water stands before and after pump- 

 ing. Number of hours elapsing before ordinary level is restored 

 after pumping. 4^7. Height below the surface at which the water 

 stood when the well was first sunk, and height at which it stands 

 now when not pumped. 5. Quantity capable of being pumped 

 in gallons per day of twenty-four hours. Average quantity daily 

 pumped. 6. Does the water-level vary at different seasons of 

 the year, and to what extent ? Has it diminished during the 

 last ten years ? 7. Is the ordinary water-level ever affected by 

 local rains, and, if so, in how short a time ? And how does it 

 stand in regard to the level of the water in the neighbouring 

 streams, or sea? 8. Analysis of the water, if any. Does the 

 water possess any marked peculiarity ? 9. Section, with nature 

 of the rock passed through, including cover of Drift, if any, 

 with thickness, ga. In which of the above rocks were springs of 

 water intercepted ? 10. Does the cover of Drift over the rock 

 contain surface springs ? II. If so, are these land springs kept 

 entirely out of the well? 12. Are any large faults known to 

 exist close to the well? 13. Were any brine springs passed 

 through in making the well ? 14. Are there any salt springs in 

 the neighbourhood ? 15. Have any wells or borings been dis- 

 continued in your neighbourhood in consequence of the water 

 being more or less braciis h ? If so, please give section in reply 

 to query No. 9. 16. Kindly give any further information you 

 can. 



PENDING PROBLEMS OF ASTRONOMY^ 

 '"THIRTY-SIX years ago this very month, in this city, and 

 near the place where we are now assembled, the American 

 Association for the Advancement of Science was organised, and 

 held its first meeting. Now, for the first time, it revisits its 

 honoured birthplace. 



Few of those present this evening were, I suppose, in atten 

 dance upon that first meeting. Here and there, among the 

 members of the Association, I see, indeed, the venerable faces 

 of one and another, who, at that time in the flush and vigour of 

 early manhood, participated in its proceedings and discussions ; 

 and there are others, who, as boys or youths, looked on in silence, 

 and listening to the words of Agassiz and Peirce, of Bache and 

 Henry, and the Rogers brothers and their associates, drank in 

 that inspiring love of truth and science which ever since has 

 guided and impelled their lives. Probably enough, too, there 

 may be among our hosts in the audience a few who remember 

 that occasion, and were present as spectators. 



1 Address to the American Association for the Advancement of Science at 

 Philadelphia. September 5. by Prof. C. A. Young. Professor of Astron >my 

 at Princeton, retiring President of the Assiciation. We are indebted to the 

 courtesy of the editor of Science for an early cjpy of Prjf. Young's address. 



But, substantially, we who meet here to-day are a new 

 generation, more numerous certainly, and in some respects 

 unquestionably better equipped for our work, than our prede- 

 cessors were, though we might not care to challenge comparisons 

 as regards native ability, or clearness of insight, or lofty purpose. 



And the face of science has greatly changed in the mean- 

 time ; as much, perhaps, as this great city and the nation. One 

 might almost say, that, since 1848, "all things have become 

 new " in the scientific world. There is a new mathematics and 

 a new astronomy, a new chemistry and a new electricity, a new 

 geology and a new biology. Great voices have spoken, and 

 have transformed the world of thought and research as much as 

 the material products of science have altered the aspects of 

 external life. The telegraph and dynamo-machine have not 

 more changed the conditions of business and industry than the 

 speculations of Darwin and Helmholtz and their compeers have 

 affected those of philosophy and science. 



But, although this return to our birthplace suggests retro- 

 spections and comparisons which might profitably occupy our 

 attention for even a much longer time than this evening's session, 

 I prefer, on the whole, to take a different course ; looking for- 

 wards rather than backwards, and confining my.-elf mainly to 

 topics which lie along the pathway of my own line of work. 



The voyager upon the Inland Sea of Japan sees continually 

 rising before him new islands and mountains of that fairy-land. 

 Some come out suddenly from behind nearer rocks or inlets, 

 which long concealed the greater things beyond ; and some are 

 veiled in clouds which give no hint of what they hide, until a 

 breeze rolls back the curtain ; some, and the greatest of them all, 

 are first seen as the minutest specks upon the horizon, and grow 

 slowly to their fiml grandeur. Even before they reach the 

 horizon line, while yet invisible, they >ometimes intimate then- 

 presence by signs in sky and air ; so slight, indeed, that only 

 the practised eye of the skilful sailor can detect them, though 

 quite obvious to him. 



Somewhat so, as we look forward into the future of a science, 

 we see new problems and great subjects presenting themselves. 

 Some are imminent and in the way, — they must be dealt with 

 at once, before further progress can be made ; others are more 

 remotely interesting in various degrees ; and some, as yet, are 

 mere suggestions, almost too misty and indefinite for steady 

 contemplation. 



With your permission, I propose this evening to consider 

 some of the pending problems of astronomy, — those which seem 

 to be most pressing, and most urgently require solution as a 

 condition of advance ; and those which appear in themselves 

 most interesting, or likely to be fruitful, from a philosophic point 

 of view. 



Taking first those that lie nearest, we have the questions which 

 relate to the dimensions and figure of the earth, the uniformity of 

 its diurnal rotation, and the constancy of its poles and axis. 



I think the impression prevails that we already know the 

 earth's dimensions with an accuracy even greater than that 

 required by any astronomical demands. I certainly had that 

 impression myself not long ago, and was a little startled on being 

 told by the superintendent of our " Nautical Almanac " that the 

 remaining uncertainty was still sufficient to produce _ serious 

 embarrassment in the reduction and comparison of certain lunar 

 observations. The length of the line joining, say, the Naval 

 Observatory at Washington with the Royal Observatory at the 

 Cape of Good Hope is doubtful — not to the extent of only a few 

 hundred feet, as commonly supposed, but the uncertainty amounts 

 to some thousands of feet, and may possibly be a mile or more, 

 probably not less than a ten-thousandth of the whole distance ; 

 and the direction of the line is uncertain in about the same 

 degree. Of course, on those portions of either continent which 

 have been directly connected with each other by geodetic triangula- 

 tions, no corresponding uncertainty obtains ; and as time goes 

 on, and these surveys are extended, the form and dimensions of 

 each continuous land-surface will become more and more perfectly 

 determined. But at present we have no satisfactory means of 

 obtaining the desired accuracy in the relative position of places 

 separated by oceans, so that they cannot be connected by chains 

 of triangulation. Astronomical determinations of latitude and 

 longitude do not meet the case ; since, in the last analysis, they 

 only give at any selected station the direction of gravity relative 

 to the axis of the earth, and some fixed meridian plane, and do 

 not furnish any linear measurement or dimension. 



Of course, if the surface of the earth were an exact spheroid, 

 and if there were no irregular attractions due to mountains and 

 valleys and the varying density of strata, the difficulty could be 



