Feb. 17, 1 881; 



NATURE 



0^0 



Aurcral Phenomena 



It is perhaps worth a note that my daughter saw at Folke- 

 stone a very unusual phenomenon on the evening of January 25, 

 a little before 6.30. Some distance to the left cf Orion (for the 

 night was clear and starry) she oljserved a small cloud of a 

 bright golden hue, from which streamers of great brdliancy 

 darted in various directions, the cloud alternately paling and 

 brightening. She describes the streamers as like small meteors, 

 leaving trails of light behind them. C. M. Ingleby 



AthenKum Club, February 12 



Ozone 



In reply to Mr. Capron (Nature, vol. xxiii. p. 219) the fol- 

 lowing explanation may perhaps serve : — 



On a flat piece of brass two strips of paper are laid, one plain 

 white, the other prepared. With a clean camel-hair brush they 

 are moistened liberally with pure alcohol. This is then burnt 

 off, firing it with a spirit flame ; the plain paper remains dear 

 and white, the prepared pajjer (beginning at the edges) gradually 

 changes to a purple brown. On immersing both strips in clean 

 water the plain paper still remains white, prepared paper changes 

 to a deep yjurple (No. S, Negretti's scale). 



In about an hour this deep purple colour fades away precisely 

 in the same way as if the slip had I'cen ozonized by exposure for a 

 day or two to the air. It may be added that if the prepared slip 

 is not plunged into water the purple brown tint remains for 

 several days. 



The experiment suggested by Mr. Capron has been made, 

 using a very delicate gold-leaf electrometer. When this is un- 

 charged there is no apparent effect ; when charged either directly 

 or inductively with either positive or negative electricity the 

 gold leaves collapse, the charge appearing to be dissipated with 

 the flame. 



I may add, when the leaves are rharged the alcohol is lighted 

 on the plate of the electrometer with a glass rod dipped in alco- 

 hol, care being taken to prevent the discharge by conduction. 

 The above experiments have been performed in an ordinary 

 study, but I cannot say they are very conclusive. 



Mr. Capron states "ozone is very strong just now," and he 

 obtains No. 10 (Negretti's scale) at an inland town. This is a 

 very high number. I have repeatedly obtained this number at 

 Hunstanton on the Wash (Norfolk), where I made experiments 

 daily for a month. The ozone cage was kept in the shade, a 

 fine cloudless day with cold north east wind blowing, and one 

 day's exposure. I have been engaged for some years in testing 

 for ozone on the coast to see if its abundance, or deficiency, is in 

 any way dependent on the physical and geological conditions of 

 the shore. My experiments are not sufSciently advanced to be 

 published, but the three following conditions have always been 

 found to be present where ozone is abundant. 



1. A long sandy shore exposed for some hours to the sun's 

 rays. 



2. Cloudless sky, with cold north or ea>t wind. 



3. An abundance of phos-phorescent light from the presence 

 of Noctiliica miliaris with the evening flow of tide. 



This town is singularly deficient in ozone. After numerous 

 experiments I have as yet only obtained No. i (Negretti's scale). 

 Whether this deficiency may not have some connection with our 

 notoriously great infantile mortality of the autumn is a question 

 for further consideration. J. P. 



Leicester, January 27 



Citania 



I HAVE not had an opportunity of reading Nature for some 

 time, but I am told that in a late number there is fome mention 

 of a so-called " Pompeii " near Eraga in Portugal. 



I do not presume to write as a learned antiquarian ; but having 

 lived for some years within thirty miles of Citania, and having 

 often visittd the place and examined the ruins with a wish to 

 gain some explanation of their mystery, I venture to write as an 

 ordinary witness. 



In no sen.'e can Citania be dercribed as a Celtic Pompeii ; it is 

 merely a collection cf circular buildings erected so close to each 

 other as almost to touch, and grouped on the top of a hill which 

 nms out as a spur from the higher ground behind it, and over- 

 looks the rich valley 1 eneath it. The vails have fallen, and the 

 stones which composed them remain /« situ, generally visible, 

 though more or less overgrown with grass. From the founda- 



tions it seeius that these round houses must have bten some ten 

 feet in diameter internally, with walls eighteen inches thick. 

 The original height of the walls may be inferred, from the 

 quantity of stones fallen, to have been some twelve or fifteen 

 feet. 



My utmost examination discovered scarcely anything beyond 

 some shattered bits of coarse pottery. But over the surface of 

 the hill there are still lying about many well-shaped round stones 

 about twenty inches in diameter, which I always thought to be 

 hand millstones. These seemed to me to afford the most likely 

 solution of any mystery connected v\ ith the place, and I inferred 

 it was a place of security, to which the corn of the district round 

 was carried. The ajiparent absence of water forbade the suppo- 

 sition that it was a place of permanent abcde. I never could 

 see any necessity for referring its origin to Celtic time. The 

 buildings were probably used, and possibly only date from much 

 later d.iys. Remembering the condition of that district as being 

 the debatable ground lying between the Asturian kingdom in the 

 north and the moors in the south, and open to sudden and tran- 

 sient incursions from either side, the utility of such a place to 

 the farmers of that district seems evident. A Portuguese gen- 

 tleman, whose name I forget, has so far interested himself in the 

 place as to rebuild one of the circular buildings in what he con- 

 ceives its original condition, and inside he has collected any 

 remains of antiquarian interest that he could scraye together. 

 Unforumately his enthusiasm for forming a kind of local museum 

 has led him to carry to it what never belonged to the place. For 

 outside his museum there is a large granite slab, which in cha- 

 racter is utterly foreign to the place, and long mystified me. 

 This " Pedra Formosa,'' as it is called by the neighbouring 

 villagers, is about nine or ten feet long, six feet high, with an 

 average thickness of one foot, and must m eigh six or seven tons. 

 It looks like a pretentious yj/forff stone, which has survived the 

 building to which it was once attached. It has some carving 

 about it, and signs v hich may or may not have any meaning in 

 them. But whatever the stone was, it has no right to be where 

 it is ; for one day, in a conversation with a local farmer at the 

 inn in the valley, I learnt the fact that some years ago all the 

 farmers of the neighbourhood combined, and yoking thirty-nine 

 pair of bullocks together, dragged the said stone from the valley 

 below, where from time immemorial it had been Ij'ing, and 

 added it in triumph to the other objects of the museum. 



I may add that during my stay in Portugal I corresponded 

 with the late Senhor Herculano, the Portuguese historian, on the 

 subject, and I believe I have stated his conclusions. 



R. Burton Leach 



Sutton Montis Rectory, Castle Cary, Febraary 8 



The Recent Severe Weather 



Your correspondent H. W. C. in his communication on the 

 above in Nature, vol. xxiii. p. 329, quotes Mr. Lowe's theory 

 of an eleven-year cycle of "great frosts," and after giving the 

 dates upon which that theory is apparently based, says : "There 

 are sorce variations in the lengths of the intervening periods, 

 but there is a distinet recurrence of eleven-year epochs^ 



With the first part of this sentence I quite agree, but I fail to 

 see the very least ground for the latter part of it, the intervals 

 taken in order being as follows: — 9, 3, 6, 18, 3, 16, 4, and 10 

 years. Three intervals approximating to eleven years can be 

 "screwed" in by manipulating the years between which you 

 reckon, disregarding inconvenient ones and using others which 

 suit better ; but surely this cannot be held sufficient to justify 

 the statement, such a method of dealing with the figures being, 

 it is scarcely necessary to point out, quite unallowable. 



I have noticed before that when the discovery of similar 

 epochs for abnormal heat, cold, rain, &c. .have been announced, 

 a similar method of dealing with dates has been fcUowed to that 

 which seems to have been adopted in this case. F. M. S. 



February 3 



The epochs which show recurrence are obtained by "manipu- 

 lating " the figures in the following manner : — 

 December iSoi to January 1814, interval 12 years 2 months. 

 ,, iSio ,, 1820, ,, 9 ,, 2 ,, 



,, 1S40 ,, 1861, ,, 20 ,, 2 ,, 



(It should here be remarked that a long but not "great" 

 frost was experienced in the winter of 1849-50; as it was not 

 severe enough to entitle it to the designation of great frost it was 



