374 



NATURE 



[January 19, 191 1 



The letters appended to the memorial are from the 

 following : — 



Astrophysical 



covo Observatory, 

 Observatory of 



(i) Directors 0/ Astronomical and 

 Observatories. 



Sir David Gill, President of the Royal Astronomical 

 Society, formerly Director of the Royal Observatory, Cape 

 of Good Hope 



Prof. Pickering, Director of the Harvard College 

 Observatory, U.S.A. 



Dr. Hale, Director of the Mount Wilson Observatory, 

 U.S.A. 



Dr. Backlund, Director of the Pou 

 Russia. 



Prof. Ricc6, Director of the Royal 

 Catania and Etna, Italy. 



Dr. Deslandres, Director of the Astrophysical Observa- 

 tory, Aleudon, Paris. 



Prof. Max Wolf, Director of the Astrophvsical Observa- 

 tory, Heidelberg. 



(2) Directors 0/ Meteorological and Physical Institutes. 

 Dr. von Hann, formerly Director of the Meteorological 

 Institute, Vienna. 

 Prof. Kayser, Director of the Physical Institute, Bonn. 

 Dr. Steen, Vice-President of the Meteorological Institute, 

 Kristiania. 



(Copy.) 



34 De Vere Gardens, 



Kensington, 

 London, W., 

 November 14, 1910. 

 Dear Lockver, — 



At j'our request I have visited, in company with your 

 son, the site at Caterham to which you propose that' the 

 instruments at present mounted at South Kensington 

 should be transferred. As the result of this inspection I 

 venture to express my earnest desire that advantage should 

 be taken of this most favourable site. 



It would be hard, in my opinion, to find a better one in 

 England. It is about 800 feet above sea-level, and over- 

 looks a wide and splendidly clear horizon. It is within 

 half an hour's walk of a railway station, and thence within 

 less than an hour's journey, by frequent trains, to Charing 

 Cross. The site is completely protected from the glare of 

 light from any neighbouring town, so that one great 

 desideratum for stellar work, that of a dark sky, is 

 secured. The contour of the neighbouring ground is such 

 as to secure immunity from the danger of houses being 

 built in the immediate neighbourhood. The surrounding 

 slopes are covered by trees which protect the surface of 

 the soil from the sun's heat, so that it is probable that 

 the disturbance to good seeing, caused by convection 

 currents, will probably be reduced to a minimum. 



It is, I believe, a general experience in this country 

 that the best definition for solar observation occurs in the 

 early morning hours, and sometimes again in the late 

 afternoon. This seems to be due to the comparative 

 freedom from convection currents of air, in the morning 

 before the soil is heated up, and in the evening when a 

 condition of equilibrium is established, and it seems, so 

 far as can be judged from inspection of the site, that the 

 surroundings of the Caterham site are specially favour- 

 able from this point of view. There are other circum- 

 stances which point to the selection of the Caterham 

 site : — 



(i) The ground belongs to the Crown. 



(2) It is distant from any roads, and therefore free from 

 tremor. 



(3) The atmosphere is free from smoke, and the site 

 above low-lying mist. 



(4) It is the site of a now disused Ordnance store for 

 ammunition, provided with splendidly built and perfectly 

 dry casemates, which would form rooms of nearly uniform 

 temperature that could be used for spectroscopic research, 

 dark-rooms, &c., and there are other existing buildings 

 which could be utilised for observatory purposes, such as 

 stores and working rooms. 



(5) The casemates themselves would afford, on their 

 upper surface, splendid foundations for instruments. 



(6) There rs excellent local material on the ground suit- 

 able for concrete. 



NO. 2 15 I, VOL". 85] 



Thus the expense of establishing the observatory would 

 be greatly reduced by these pre-existing works and by the 

 natural facilities afforded by the site. 



I have no doubt that the Meteorological Office can 

 furnish statistics as to the average amount of cloud and 

 sunshme, and little doubt that in this respect the con- 

 ditions are as favourable as any for the pursuit of Astro- 

 physical and Solar research. 



That it is the duty of our country to provide for the 

 continuity of the work so well begun bv you I think no 

 man of science will dispute, and it would indeed be shame 

 to us, in the face of what other nations are doing, if \\v> 

 are left behind in the race which was so well begun 

 this country by yourself, and which has been contin 

 by you so successfully under conditions so unfavouns 

 In any change of site I venture to think it will b- 

 great mistake if the best possible site is not chosen, ; 

 1 do not think it is likely that a better site than that 

 Caterham will be found in these islands. 

 Yours sincerely, 



(Signed) David Gill. 



(Copy.) 



Harvard College Observatory, 



Cambridge, Mass., 



November 4, 1910. 

 My Dear Sir Norman, — 



Your letter of October 20 is received. I hear with great 

 regret of the unfavourable changes which are proposed in 

 the Solar Physics Observatory. The list of your publica- 

 tions and of the important results contained in them is 

 very impressive. It seems to me that your persevering 

 and long-continued work in astronomy, extending over 

 nearly half a century, ought to be continued by you under 

 favourable conditions, if possible. Moreover, it is obvious 

 that the efficiency of the powerful instruments which you 

 have collected will depend very largely on the location in 

 which they are remounted. Every year this matter is I 

 receiving more attention among astronomers. The work I 

 of many instruments could easily be doubled by mounting 

 them in more favourable locations. The most serious 

 effect we have felt from the encroachment of the city of 

 Boston has been the illumination of the sky by the electric 

 light. 



Yours very truly, 



(Signed) Edward C. Pickering. 



The Athenaeum, 



November 7, 1910. 

 My Dear Sir Norman, — 



You ask me for an opinion as to the value of the work 

 done under your direction at South Kensington, and the 

 importance of providing for its continuance under mor' 

 favourable conditions. As you know, I have not alw^v 

 agreed with you as to methods of observation and 1; 

 interpretation of results. But this has not prevented r, 

 from admiring your fertility and ingenuity in the formul 

 tion of hypotheses, and the activity of yourself and yo. 

 assistants in testing them. The large amount of wo: 

 done by your staff in the midst of- London should encourn^ 

 those who see in the establishment of large mode- 

 observatories a menace to smaller institutions. 



The importance of providing for the Solar Physi' 

 Observatory in the future seems to me so obvious that 

 can hardly believe the Government will fail to do s- 

 After permanence has been assured, the most vital poin 

 in my opinion, is to discover a sufficiently able direct- 

 to take up the work when you retire. Then come tl 

 exceedingly important questions of site and equipment, 

 cannot compare the merits of the two sites you mentio: 

 as I have not seen the one you prefer and you do n< 

 name the other. Other things being equal, high altitud- 

 minimum cloudiness, a clear and transparent sky, absern 

 of glare from street lights, and freedom from vibratio 

 are, of course, very important. 



But the prime consideration is good definition of soln 

 and stellar images, without which the most refined wor'- 

 cannot be done, in certain classes of observations. 



You refer to the need of a clear eastern horizon. O' 

 Mount Wilson (altitude, 6000 feet) it is essential that th' 



