March 13, 1884] 



NA TURE 



471 



lous ! The Editor of Nature writes on December 20 (p. 174), 

 with an enthusiastic glow worthy of the twiUghts : " The extra- 

 ordinary fact now co.nes out that before even the lower currents 

 had time to carry the volcanic products to a region so near the 

 eruption as India, an upper current from the east had taken them 

 in a straight line via the Seychelles, Cape Coast Castle, Trinidad, 

 and Panama, to Honolulu, in fact very nearly bade again to the 

 Straits of Sunda ! " [The note of admiration is not mine]. 

 It is worth our while to calculate the rate at which this wonder- 

 ful journey of volcanic dust was performed. The actual distance 

 is 255° of a gi-eat circle, and the time of journey nine days, from 

 which I calculate the speed of the train to have been eighty-two 

 miles per hour ! This is absolutely incredible, and becomes 

 still more so when we know that the phenomena observed at 

 Honolulu were unusual twilight phenomena, but had no connec- 

 tion whatever with reflection from the upper rei;ions of the air. 

 In point of fact, my calculation of the sun's position disproves 

 the presence cf dust or any reflecting substance in the upper 

 air. Observation II. Dunsink Observatory {a letter received 

 from Dr. R. S. Ball, F.R.S., January 7, lS';4) :—" Sunday 

 evening, December 30, was exceptionally fine, and the sunset 

 was so well seen, that the moon, though only twenty-seven hours 

 old, was well seen by Cathcart and myself from the roof of the 

 Observatory. We estimated that the twilight lasted certainly 

 for two hours after sunset, and that for ten minutes longer there 

 was still enough light in the western sky to dislinguisli it from 

 other parts of the horizon. At two hours the sun's zenith distance 

 is 15° 56'; at two hours and ten minutes it is 16° 51'. The first 

 figure coincides almost exactly with the 15° 51' given by that 

 most skilful observer Schmidt (vide Asiron. Nach , .No. 1495), of 

 Athens, as the zenith distance at the end of astronomical twilight. 

 The 18° which the text-books state to be the limit, seems to be 

 a sun'ival from Kepler, who had it from Ptolemy. There seems 

 to be rather a dearth of careful observations on the subject, at least 

 lean find but few good references to it in Yiawi&'m^'s, Astronomy. 

 The only one of this century there contained besides Schmidt is 

 Liais' {Comptes Rendus, t. xlviii. p. no) ; he says tiiat the first 

 'arc crepiisculaire ' sets at li°42', and the second at 18" 18'. 

 It appear; to me that on the whole the truth lies nearer 

 to 16° than to any other figure." Observation III. (a letter re- 

 ceived from Mr. R. S. Graves, Kingstown, Co. Dublin, December 

 26, 1S83) : — " I was on Kingstown Pier yesterday evening (25th 

 inst.), and as the after-glow of sunset looked so beautiful behind 

 the hill, I lingered on the pier, looking at the wonderful bright- 

 ness and beauty of the whole west sky. The red glow continued 

 to throw distinct light on the harbour's shipping till 5.20 ; from 

 that time, however, the light faded very fast, and at 5.30 it was 

 black night, although the sky was still very red. After this 

 hour the light-giving power seemed to have gone. I see the sun 

 set at 3.53 p.m. (Dublin almanac). The lights in Kingstown pre- 

 sented a very curious appearance : looking at the bright red 

 above the hill, then the hill, and under the hill the hundreds of 

 lights looked just like one of those fancy foreign pictures with 

 pinholes stuck in everywhere to represent the lights. I wish you 

 could have seen the whole scene." N.B. The sun was 14° 15 

 below horizon at close of phenomena. Observation IV. (a letter 

 received from a correspondent in Old Derrig, Co. Carlow, 

 December 31, 18S3) : — ". . . I have, of course seen a good 

 deal of the after-glow. Some evenings the appearance is like 

 the glare of limelight at a theatre, the effect on grass or garden 

 very strange. With back to west each blade of grass is like 

 fire, a bit of straw like a red-hot needle ; but facing the light, it 

 is all lurid light and shade. Last night sun set by almanac at 

 3.47 ; here the sun disappears twenty and twenty-five minutes 

 before, owing to hills. At 4.30 the glow was splendid ; at 5.10 

 I could see seconds-hand of watch 23 minutes after sunset, or 

 nearly l| horn- after sun had vanished from us, A planet from 

 4.30 to 5.10 was in the glow, and from 5 and 5.30 was bright 

 emerald green." N.B. The sun was 15" 15' below horizon at 

 close of phenomena. — Prof. W. R. McNab, M.D., read 

 a paper entitled: "Note on the botanical topographical divi- 

 sions of Ireland." The districts adopted by the authors of the 

 " Cybele Hibernica" not being readily comparable with the 

 diWsions into provinces, vice-provinces, and vice-counties, as 

 defined by Watson, it is proposed to treat the "districts" as 

 equivalent to provinces, and to arrange thirty-six vice-counties 

 under the twelve provinces. The divisions Dr. McNab thus 

 proposes to adopt in the " Cybele Hibernica " collection at 

 Glasnevin, Dublin, are the following : — Province I. West 

 Munster. — Vice-counties : l. Kerry. 2. S. Cork. H. East 



Mnnster.— (3) N. Cork ; (4) Waterford ; (5) S. Tipperary. III. 

 West Leinster. — (6) Kilkenny ; (7) Carlow ; (8) Queen's County. 

 IV. East Leinster.— (9) Waterford; (10) Wicklow. V. North 

 Leinster. — (11) Kildare ; (12) Dublin; (13) Meath ; (14) Louth. 

 VI. West Shannon. — (15) Limerick; (16) Clare; (17) East 

 Galivay. VII. East .Shannon. — (18) North Tipperary; {19) 

 King's County ; (20) Westmeath; (21) Longford. VIII. West 

 Connaught. — (22) West Galway ; (23) West Mayo. IX. East 

 Connaught. — (24) East Mayo ; (25) Sligo ; (26) Leitrim ; (27) 

 Roscommon. X. South Ulster. — (28) Fermanagh ; (29) Cavan: 

 (30) Monaghan ; (31) Tyrone ; (32) Armagh. XL West Ulster. 

 — (33) Donegal, and City of Londonderry. XII. Ea>t Ulster. — 

 (34) Down; (35) Antrim; (36) Derry.— Prof. A. C. Haddon 

 communicated a paper on an apparatus for demonstrating sys- 

 tems of classification, &c. — The apparatus, which was exhibited 

 last March, consists of a series of glass plates placed horizontally 

 one over the other, leaving a small space between each plate. 

 On these plates oblong blocks of wood rest on which are printed 

 the names of the forms whose affinities it is desired to indicate, 

 thus constituting a classification in three dimensions of space. 

 This apparatus is especially useful in paleontology. 



Paris 

 Academy of Sciences, March 3. — M. RoUand in the chair. 

 — Re-earches on explosive gaseous mixtures, by MM. Bertlielot 

 and Vieille. The results are here tabulated of 250 experiments 

 made with forty-two distinct explosive compounds, including 

 not only mixtures of oxygen and hydrogen, the oxide of carbon 

 and formene, pure or mixed with nitrogen, but also mixtures in- 

 cluding cyanogen, acetylene, etliylene, methyl, methyI;-» ether, 

 and common vapour of ether. Studies were also made of mix- 

 tures of oxygen with two combustible gases together, such as the 

 oxide of carbon and hydrogen, as well as combinations of the 

 protoxide of nitrogen mixed with hydrogen, with the oxide of car- 

 bon, with cyanogen, and the bioxide of nitrogen mixed with cyano- 

 gen. The main object of the experiments was to determine the 

 amount of pressure developed at the moment of explosion, the tem- 

 perature produced, and the specific heats of the gases at various 

 temperatures, and especially those of the compound gases. — On 

 a recent note of M. D. Andre, by Prof. Sylvester. It is shown that 

 M. Andre's theorem is a direct consequence of the generalisation 

 given by the author to Newton's theorem (" Universal Arith- 

 metic," part 2, chap, ii.) on the imaginary roots of equations. — 

 Remarks on the maps of Madagascar from the Middle Ages to 

 the present time, by M. Alf. Grandidier. The author, who 

 identifies Ptolemy's .Menuthias with Madagascar, shows that this 

 island was known to the Greek and Arab geographers long before 

 its rediscovery by the Portuguese in 1500 (not in 1506 as is usually 

 supposed). — On the principle of separate watertight compart- 

 ments in ship-huilding, and on the first men-of-war constructed 

 on this principle, by M. Bertin. — New experiments showing how 

 Nobili's electro-chemical rings may be imitated by means of a 

 continuous stream of water falling from a cylindrical tube verti- 

 cally on a horizontal sheet of black glass moistened all over, by 

 M. C. Decharme. — Description of a new process of generating 

 steam, by M. Bordone. — Theorem by means of which it may be 

 ascertained that certain algebraic equations have no positive root, 

 by M. Desire Andre. — Note on hyperfuchsian functions, byM. E. 

 Picard. — On the [groups of finite order contained in the group 

 of imdeterminative and reversible substitutions of the second 

 order, that is, the quadratic substitutions of Cremona, by M. 

 Autonne. — On linear equations of the second order with partial 

 differences, by M. R. Liouville. — Note on the oxychloride of 

 barium, by M. G. Andre. — On a new group of nitrous com- 

 pounds, by M. R. Engel. — On the oxidation of menthol by 

 means of the permanganate of potassium, by M. G. Arth. — On 

 two campholurethanes with an isomerous relation analogous to 

 that presented by M. Pasteur's right and left tartaric acids, byM. 

 Haller. — Experiments on the toxic or medicinal substances 

 which modify haemoglobin, and especially on those that 

 convert it into methsemoglobin, by M. G. Hayem. — On the 

 conditions favourable to the development of root-suckers in 

 plants, by M. E. Mer. — Ai alysis of the mineral substances 

 friedelite, discovered by M. Bertrand, and pyrosmalite, found 

 at Dannemora in Sweden, by M. Alex. Gorgeu. — Note on the 

 existence of manganese in a state of complete diffusion in 

 the blue marbles of Carrara, Paros, and the Pyrenees, by M. 

 Dieulafait. — On the coincidence of the transformations observed 

 in the Pons-Brooks comet with its passage across currents of a 

 cosmic character, by M. Chapel. — Notice of two Chinese works 



