412 



NA TURE 



[April i, 1922 



each other. They moreover make equal angles 

 of '2.^\° (or a sixteenth of a circle) with the cross 

 centre line of Stonehenge. 

 This symmetry is very striking, and is so complete 



Fig. 2. — Stone No. 91. To south-east. 



that it cannot be accounted for as a mere coincidence. 

 It obviously points to the conclusion that the Four 

 Stations, Nos. 91 to 94, were all specially located in 

 relation to one another as parts of one scheme to 

 serve some definite purpose in the general design of 

 Stonehenge. 



Fig. 3. — Stone No. 93. To north-west. 



On this Flinders Petrie remarks : — 



" On examining the stones and mounds 91 to 

 94 on the earth bank it will be seen that they are 

 exactly opposite, stone to stone, and mound to 

 mound. This strongly shows that they are con- 

 temporaneous ; as is also shown by the fact that 

 the diameters joining their centres cross each other 



at . . .just half a right angle ; and further the 

 diameters are complementary to each other, being 

 symmetrical about the axis of the structure " 

 (" Stonehenge," p. 21). 



We cannot doubt that at one time there was a 

 stone in each of the positions now indicated by the 

 two mounds ; and that, whatever the purpose of the 

 arrangement may have been, it had nothing to do 

 with the neighbouring Round Barrows. 



The two stones (Nos. 91 and 93), now in place, are 

 shown in the accompanying photographs (Figs. 2 and 3) . 

 It will be observed that the ground is level around 

 the base of each stone. 



The two mounds (Nos. 92 and 94) are of very slight 

 elevation, and are scarcely noticeable on the ground. 

 Assuming that each of these two sites had at one time 

 been occupied by a stone, we may suppose that the 

 small amount of earth forming the present mound 

 was thrown out of the excavation made when the 

 stone was removed. When, later on, the cremated 

 interment was buried, the incipient mound was per- 

 haps trimmed up and added to. 



It may be considered certain that the Four Stations 

 were in no way connected with the "Aubrey Holes," 

 and that they belong to a different period of Stone- 

 henge history. ^ Herbert Stone. 



The Retreat, Devizes. 



Improvement of Visibility of Distant Objects. 



In connection with the subject of some recent 

 letters in Nature on " A Method of Improving Visi- 

 bility of Distant Objects " by Prof. C. V. Raman 

 (October 20, 1921) and by Mr. A. G. Lowndes and 

 Sir David Wilson-Barker (November 10, 1921), it 

 may be of interest to mention that two years ago I 

 published a complete essay on the same question in 

 the French Bulletin Officiel de la Direction des 

 Recherches Scientifiques et industrielles du Ministdre 

 de ITnstruction Publique, No. 4, February, 1920, 

 pp. 229-48, under the title " Sur rutilit6 de la lumidre 

 polarisee dans les observations faites en mer ou au 

 bord de la mer, et sur une jumelle a polariseurs." 



Every advantage of polarised light mentioned by 

 your correspondents, such as improvement of optical 

 contrasts, visibility of colours in distant objects, etc., 

 was considered and discussed in detail in that paper. 

 I must mention that I took the research in hand in 

 1916 for military purposes, in connection with the 

 French Ministry of Invention and Research and with 

 the French Admiralty. The results and my former 

 reports were communicated to the English Board of 

 Invention and Research (1917). A little later. Prof. 

 W. F. Durand, of Leland Stanford University, then 

 the Scientific Attache to the American Embassy in 

 Paris, having been kind enough to order the transla- 

 tion of my reports into English, that English version 

 was given likewise to the official agent of the British 

 Ministry of Munitions Optical Department, Mr. F. C. 

 Dannatt, now representative of the British Scientific 

 Apparatus Manufacturers, Ltd., in Paris. At the 

 end of the war the French Navy had a small number 

 of binoculars equipped with spar polarisers of the 

 Glazebrook-Ahrens type cemented with a special 

 oil, as described in my paper. The constructor, 

 M. A. Jobin, member of the French Bureau des 

 Longitudes, supplied a few of those binoculars, at 

 the recjuest of the British Government, through Mr. 

 Dannatt. 



I do not wish to take up the space available in 

 Nature with a translation of my paper, but a short 

 summary of a few of my conclusions may be of 

 interest. 



Contrary to Mr. Lowndes's opinion, I objected very 



NO. 2735, VOL. 109] 



