4 r H 



NA TURE 



{Sept. 



Fireballs 



In addition to the occurrences recently recorded in your 

 columns, it may be well to quote a further observation communi 

 cated in a letter, by Lady Borthwick, to the Morning Post for 

 August 16, dated from Derculich, Ballinlaig, Perthshire, from 

 which I extract the following particulars : — 



As several curious phenomena of a like kind had been described 

 as having occurred in Edinburgh during a terrific thunderstorm 

 on Tuesday, August 12, the writer proceeds to detail what had 

 been witnessed by herself and some others in her neighbourhood. 

 The storm began at 10 o'clock in the morning and continued 

 with unabated violence till past 10 at night. It appeared to be 

 at its height from about 3 till 7 p.m., when as many as three 

 flashes of lightning occurred to one peal of thunder. In many 

 cases they were of a vivid pink colour. At about 6 o'clock a 

 loud noise was heard, unlike any preceding it : " the heavens 

 seemed to open, and there issued from the clouds what appeared 

 like a ball of fire, about the size of a man's head, which exploded 

 with a terrific crash, emitting quantities of sparks." It then 

 appeared to descend at a distance of not more than twenty yards 

 from the house. Mr. J. K. Laughton, commenting upon the 

 phenomenon in the next issue, states that " ball lightning " is 

 not solid, but yet in "passing along the surface of soft land it 

 ploughs it up in a way that no cannon ball could do," and refers 

 to an instance of this mentioned by Scott in his "Elementary 

 Meteorology." 



At a recent meeting of the Paris Academy of Sciences, M. 

 Gaston Plante illustrated some remarks upon globular electric 

 bolts by producing artificially effects analogous to those of fire- 

 balls, and it would be interesting to know more respecting their 

 nature. As they appear to occur only very occasionally, on 

 account of the rare conditions of the atmosphere producing them, 

 it is certainly advisable to collect all the evidence respecting 

 them that is obtainable. By such means it may in the course of 

 time become possible for those who are competent to deal with 

 the facts, to arrive at some definite conclusions concerning this 

 little understood phenomenon. Wit. White 



September 2 



Deep-Sea Corals 



Prof. H. N. Moseley, F.R.S., in his masterly address to 

 the Biological Section of the British Association at Montreal, 

 dealt, amongst other matters, with the zoological position of the 

 remarkable genera of deep-sea corals named Guynia, nobis, and 

 Haplophyllia anil Duncania, of Pourtales. He states that he 

 has found, after examing sections of the last-named genus, that 

 the soft parts indicate that it and the others are Hexactinia, and 

 have the construction of Caryopkyllia and of all other corals of 

 that group. These genera were placed amongst the Rugosa, 

 the first-mentioned by myself fourteen years since, and the 

 others by Pourtales later on. On April 3 of the present 

 year I read a communication to the Linnean Society, entitled 

 "A Revision of the Families and Genera of the Madreporaria," 

 and this revision is published. As Prof. Moseley left England 

 before I could send him a copy, he and some other naturalists 

 who study the corals will be perhaps interested by knowing that 

 I have placed those genera where Prof. Moseley has located 

 them subsequently. They form an alliance in the family Tur- 

 binolidfe, and I was led to alter the classificatory position on 

 account of a careful examination of the hard parts. 



August 30 P. Martin Duncan 



Iridescent Lunar Halos 



On the evening of July 4, from 5.30 p.m. to 7 p.m., the 

 moon, eleven days old, was surrounded with a series of extra- 

 ordinary halos consisting of a succession of concentric rings ; 

 fine, clear starlight ; very light airs from south-west and west- 

 south-west ; thermometer, 42°. 



At 5-3°, very light fleecy scud from south-west, the moon sur- 

 rounded with a halo of about three times its diameter, of dullish 

 white within a ring of orange ; rapid changes ensued : the moon 

 appeared within an opaque circle intensely white, surrounded 

 with chromatic rings in the following order — yellow, orange, 

 red, indigo, a broad ring of blue, yellow, orange, red, indigo, 

 deep blue, bordered by a faint ring of orange. At this time the 

 moon appeared as a bright boss on a many-coloured shield ; 

 changes rapidly followed : at 5.35 the rings were as follows — 

 white, yellow, orange, red, indigo, blue, yellow, orange ; for 



some moments the outer ring of orange became blurred, the 

 broad ring of blue very deep and beautiful ; at 5.50 all of the 

 halo had disappeared ; sky clear, bright starlight all round, ex- 

 cept where a few light fleecy clouds lay to the north-east. At 

 6.10 light scud from south-west ; at 6. 12 halo again formed, as 

 follows — white, yellow, orange ; in a few moments were added 

 red, indigo, blue, orange ; soon a mass of whitish scud, light 

 and fleecy, seemed to gather round the moon widely, in a huge 

 irregular oval, changing almost to a circle with uneven edges. 

 At 6.20 the halo had disappeared ; then came a bow-shaped 

 yellowish coloration on the south-west of the moon, changing 

 instantly to orange, red, indigo, faint indistinct orange ; at 

 6.22 all clear again ; at 6.29 bright almost dazzling rays im- 

 mediately surrounded or jettied from the moon. At 6.30, north 

 of the moon, orange appeared on some light scud ; soon changes 

 again took place : immediately on the edge the moon, where 

 the rays were so brilliant, was now very dark with jagged edges 

 within an intensely white ring, surrounded with a series of 

 sharply-defined chromatic rings in the order they appeared at 

 5.35. At 6.35 another mass of whitish scud widely surrounded 

 the moon as before described ; at 6.48 all clear again ; instantly 

 after an orange patch appeared on scud to the north ; at 6.56 

 orange on east ; at 7 p.m. all was again clear ; rays as dazzling 

 as at an earlier period ; temperature sensibly lower ; frost at 

 night. T. H. Potts 



Ohinitahi, N.Z., July 5 



Sextants 



In your review of the " Encyclopaedia Britannia " published 

 last week I notice that reference is made to an article on navi- 

 gation by Capt. Moriarty, and attention is called to the very 

 serious error in sextants arising from false centering. Having 

 had some experience in the examination of these instruments, 

 I can practically testify to this most important defect. Only a 

 week or so since two sextants were received here for trial, 

 one of which belonged to a captain of the mercantile marine. 

 In both instances, although the mirrors and shades were good, 

 yet the arc error due to false centering was excessively large, in- 

 creasing from o at 0° to + 7' at 6o°, while at 90 it amounted to 

 10'. Surely this must be a serious matter to navigators, but, as 

 you point out, for the small fee of five shillings persons ordering 

 a sextant may direct the maker to send it to the Observatory, 

 where suitable apparatus is arranged not only for examining the 

 arc but also the mirrors and shades. It is only fair, however, 

 to say that when instruments are sent direct from the makers we 

 do not often have occasion to reject one. Indeed, superior sextants 

 by first-class makers rarely have an error exceeding 1' of arc, and 

 often not more than 30", but how few these are in comparison with 

 the hundreds of inferior instruments that pass into the hands of 

 the public without being tested. T. W. Baker 



The Kew Observatory, Richmond, September 2 



Electrical Rainbow 



I WAS one of a deputation of River Tyne Commissioners who 

 visited the South Foreland, to see the experimental lights now 

 on trial there, on Saturday night, August 30. We were walking 

 across the fields from the lights towards the observing hut No. 2, 

 a distance of about a mile and a half. There was a fog more or 

 less, and a shower of rain as we were approaching the hut, and 

 every time the electric light from A tower revolved, a rainbow, 

 very like a faint lunar bow, made its appearance. I could not 

 see any prismatic colour, and the bow was only produced by the 

 large electric light, with carbons of I \ inch in diameter. There 

 was no bow visible from the old light, which has carbons of 

 about % inch square, and none from either the gas or oil lights. 

 I was informed that this was the first time such a phenomenon 

 had been observed. R. S. Newai.l 



Ferndene, September 3 



Rainbow on Spray 



A curious appearance, which I have never observed before, 

 was visible here for a few minutes this forenoon. Large breakers 

 were rolling in to the bay, and their fronts (covered with foam) 

 were brilliantly white in the sunshine. But, as each passed a 

 particular spot, directly opposite to the sun, the spray blown 

 back froai its crest took a bright reddish-brown colour. This 

 was the apex of the primary rainbow. When observed from a 



