March 6, 1884] 



JVA TURE 



427 



the same time we may remind Dr. Anderson that the 

 statement that the sternum in all Picarian birds has a 

 "double notch behind" (p. 94) is not quite correct, 

 and that he has overrated the number of African 

 rhinoceroses. 



Judging from the " Guide," the series of animals now 

 exhibited in the Zoological Gardens of Calcutta must be 

 considerable, although no actual statistics are furnished 

 to us on the subject. Several animals of special rarity 

 are mentioned as in the collection, such as a specimen of 

 Grant's Gazelle {Gazelle f^ranti) from East Africa, and 

 the second known example of the Hairy-eared Rhinoceros 

 of Chittagong. It is also of great importance to learn 

 that the phenomenon of incubation of one of the large 

 Pythons has been witnessed in Calcutta as well as in 

 European Gardens. On the whole, the naturalist will find 

 many things to interest him throughout the present volume, 

 though, as already said, some of the disquisitions are not 

 perhaps cjuite suitable to a popular work. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himselj responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymotis communications. 



[The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his^ space is so great 

 that it is impossible othenvise to insure the appearance even 

 of comiiiunications containing interesting and novel facts. '\ 



Earthquakes and Air- Waves 



I.v the Comptis Kendus of ihe French Academy of Sciences 

 for February 18, 18S4, there appe.-u's a commmiication from 

 Prof. Forster of Berlin relative to a statement previously made 

 in the Comptcs Kendus, to the effect that it was. from olwervations 

 taken at Berlin that he had arrived at certain conclusions as to 

 tbe propagation of the atmospberic disturbance caused by the last 

 great explosion in the eruption of Krakatoa in August last. 



Prof. Forster explains that the statement referred to was a 

 mistake, and that he had in fact only reproduced, after verifying 

 them by reference to the Berlin observations, the conclusions 

 come to by nie, as explained in a paper r, ad before the Royal 

 Society on December 17, 18S3, the principal part of which was 

 published in Nature of December 20 last (p. iSi). 



He adds that in his original note on the .'ubject he had not 

 mentioned my name as the author of the conclusions referred to, 

 in consequence of the manner in which I had spoken of them 

 myself 



Prof Forster, while putting himself right on this point, has 

 interpreted my own intention with great sagacity. For the light 

 I may have been able to throw on the facts was in truth conse- 

 quent on information put before me by the inlelligent officers of 

 our Meteorological Office, aided by a suggestion from Prof 

 Stokes, who like myself is a member of the Meteorological 

 Council. 



Such credit, however, as is due for bringing to notice the 

 curious phenomenon in question may be fairly claimed for our 

 Meteorological Office, as there is little reason to doubt that it 

 would have remained unnoticed had it not been f >r the com- 

 parison of tlie several records of the continuously self registering 

 instruments which the organisation provided from the public 

 grant we receive has placed at our command, and which no 

 individual effort could have supplied. 



February 26 Richard Strachey 



In the Jamaica Weather Report, No. 35, for November last 

 year, I was unable to explain how it was that the Krakatoa air- 

 wave had affected our barometer so strongly : the exjilanation is 

 that Jamaica is very near the antipodes of Krakatoa (Natijre, 

 vol. xxix. p. iSi). 



The general effect of the disturbance at Jamaica was to pro- 

 duce a barouietvic depression, preceded and followed by small 

 barometric elevations, according to the following table, which 

 gives for local time the pressure of the atmosphere at the sea- 



level, expressed in inches of mercury at 32^, and corrected for 

 diurnal variation : — 



Kingston, yamaica, 1883 



August 26, 3 p.m. ... ... ... 29'972 



26, II p.m. ... ... ... '975 



27, 7 a.m. ... ... ... -982 



27. 3 I'-"i '944 



27, II p. m -983 



28, 7 a.m -994 



28, 3 P-m 29-975 



Now Ihe impulse at Krakatoa occurred at 9.24a.m. local time, 

 and it reached Jamaica about 3 p.m. local time, or eighteen 

 hours afiei wards ; consequently the average velocity of the wave 

 was about 690 miles an hour — which is wholly in accordance 

 with the velocity deduced by General Strachey from places in 

 Europe and ebewhere. 



But there was no great explo-ionat Krakatoa at 9. 24 a.m., and 

 it seems possible that this great air-wave «as similar to the air- 

 waves we ahv.ays experience in Jamaica whenever there is a shock 

 in Kingston sufficiently strong to be distinctly felt. 



In August 18S1 1 published a Report on Earthquakes in 

 Jamaica, No. 4, in order to call attention to the follov\ing 

 fads : — 



1. The atmospheric pressure oscillates for some hours before 

 and after a shock, the lowest depression generally occurring at 

 the time of the shock. 



2. The wind generally lulls, so that " the weather " is h^jt 

 and oppressive. 



3. Clouds (stratus) gather over the sky after the shock. 



4. The temperature of the air, if we allow for the cooling 

 effect of (3), remains unchanged. 



5. The rainfall is unaffected. 



These facts have been fully confirmed by subsequent shocks. 

 As an example let us consider the last shock which occurred on 

 January 14 this year, and which was felt over nearly the whole 

 of the island. 



At Kingston it was felt as a sharp double-shock at 1.15 p.m. ; the 

 first shock lasted about three seconds, then there was an interval 

 of about two seconds, which was followed by the second shock, 

 lasting about five seconds. There was a strong sea-lireeze blow- 

 ing during the day, but a temporary lull occurred just before the 

 earthquake. 



The following table gives the pressure of the atmosphere at 

 the sea-level, expressed in inches of mercury at 32°, and corrected 

 for diurnal variation : — 



Kingston, January 14, 1SS4 



24 hours before the shock 



At the time of the shock 

 8 hours after 



16 ,, 



24 „ 



30-061 

 -047 



■043 

 ■016 



-024 



•063 



30-056 



On January 13 the average amount of cloud was 7 per cent, of 

 the whole sky, on the 14th it was 10, and on the 15th it was 43! 



Further parlicidars will be found in the Jamaica Weather 

 Report, No. 37, for January 18S4, and it will here be sufficient 

 to remark that the depression at the time of the shock was quite 

 as strongly marked at the cinchona plantation, thirteen miles 

 from Kingston, but 4850 feet above the sea-level. 



It is needless to say that I am at a loss to account for the con- 

 nection which most undoubtedly exists in Jamaica between 

 earthquakes and air-waves ; but it is evident that the latter may 

 be connected with the former without any, the slightest, approach 

 to volcanic explosion ; and the Krakatoa air-wave was probably 

 similar in all respects, except magnitude, to the waves we con- 

 tinually experience in Jamaica at the time of earthquake shocks. 



Jamaica, February 7 Maxwell Hall 



The Remarkable Sunsets 

 At 8.45 a.m. to-day the sun seen from here through a light 

 mist was of a slightly metallic and very pale sea-green colour. 

 The mist was not dense enough to render objects at a distance of 

 twelve yards indistinct, but beyond that distance they rapidly 

 became invisible. There was no wind, and the mist seemed free 

 Irom smoke. I could form no opinion as to its height. Half 



