Aprils, 1886] 



NA TURE 



533 



shadow, and we saw a circular rainbow of perliaps S° or 10° dia- 

 meter surrounding the shadow of the summit, and as we waved 

 our arms we saw the shadow of our limbs moving in the mist. 

 Two dark lines seemed to radiate from the centre of the bow, 

 almost in a prolongation of the slopes of the Peak, as in the 

 figure. 



Twice this shadow appeared and vanished as cloud obscured 

 the sun, but the third time we saw what has apparently struck 

 so many observers. T'le shadow seemed to rise up and stand in 

 front of us in the air, with rainbow and spectral arms, and then 

 to fall down suddenly to the earth as the bow disappeared. 

 The cause of the whole was obvious. As a mass of vapour 

 drove across the shadow, the condensed particles caught tlie 

 shadow, and in this case were also large enough to form a bow. 

 As the vapour blew past, the shadow fell to its natural level — 

 the surface of the earth. 



An hour later, when the sun was well up, we again saw the 

 shadow of the Peak and ourselves, this time encircled by a 



Shado^ 



double bow. Then the shadow was so far down that there was 

 no illusion of standing up in front of us. 



I believe that the formation of fog-bow and spectral figures on 

 Adam's Peak is not so common as the simple rising up of the 

 shadow, but one is only a development of the other. In fine 

 weather, when the condensed vapour is thin and the component 

 globules small, there is only enough matter in the air to reflect 

 the Peak shadow in front of the spectator, and no figure is seen 

 unless the arms are waved. In worse weather the globules of 

 mist are large enough to form one or two bows, according to 

 the intensity of the light. We were fortunate to see the lifted 

 shadow accompanied by fog phenomena, which left no doubt as 

 to the cause of the whole appearance. 



Any idea of mirage was entirely disproved by my thermo- 

 metric observations, which cannot be detailed here for want of 

 space. Ralph Abercromby 



Colombo, February 25 



" Bishop's Ring" 

 The critique on Dr. Riggenbach's pamphlet on the Krakalao 

 dust-glows alludes to the peculiar ring since seen surrounding the 

 sun, and known as " Bishop's Ring," as though it had ceased to 

 be visible last year. But the peculiar pink-tinged area sur- 

 rounding the sun has been constantly seen since then, though 

 perhaps without so definite a succession of tints as to deserve 

 the title of "halo." On almost any day when the sun is hidden 

 by a dense cloud so that the direct light is greatly subdued, 

 there will appear, surrounding the cloud, an area at first in- 

 tensely white, and then passing into a definite pink tinge. I 

 saw this phenomenon very markedly this afternoon at 5. 10 p.m., 

 when walking across the fields from Swinggate, a hamlet be- 

 tween here and Dover, towards the Cornhill Coastguard Station. 



I have always observed it better when there is a strong south- 

 west wind blowing. Does this mean that the great mass of the 

 dust -particles is still in equatorial regions ? Though the pheno- 

 menon to which I allude is undoubtedly best seen when the sky has 

 that gray tinge which accompanies a saturated'or super-saturated 

 condition, I can hardly think it due to moisture. I did not 

 observe it till after the Krakat.ao eruption, and I have observed 

 it constantly since that outbreak. Perhaps condensation of 

 moisture in the upper aerial regions may result in the formation 

 of minute particles of water to which the dust-particles become 

 attached, and thus both water and dust may be concerned in the 

 production of the pink-tinged area. Edward F. Taylor 

 St. Margaret's-at-CUfife, Dover, March 29 



"Ferocity of Rats " 



In reference to the correspondence that appeared in last 

 week's issue (p. 513) upon the above subject, permit me to state 

 I have found by practical experience that the ferocity and 

 voracity of rats is very great. They devour one another at all 

 times and under all circumstances, whether living in a wild state 

 or under the influence of domestication. I kept six rats at one 

 time in confinement, and although well fed, the largest specimen 

 consumed all the rest. Again, shortly after the late Inventions 

 Exhibition closed last year, the following incident came under 

 my notice, which fully confirms me in the belief I have ex- 

 pressed. As I was passing through the building I heard wild 

 and piteous cries issuing from a spot close to where I stood. I 

 immediately proceeded thence, and beheld six large rats feasting 

 upon three of their congeners not much smaller than themselves, 

 who were endeavouring to free themselves from the sharp teeth 

 of their assailants. All of these rodents appeared thin and 

 wild, and were no doubt rendered bold and desperate by priva- 

 tion, for my presence had no effect upon their carnivorous 

 attacks. I frequently hear rats scampering beneath the floor of 

 my oflice, accompanied by loud and protracted squeals ; and, 

 after what I saw, I am induced to believe that a deadly raid is 

 on such occasions being made upon one or more of them. 



W. August Carter 



The Claylands, South Norwood, April 5 



Weather in South Australia. — Stevenson's Thermometer- 

 Screen 



Lately the conditions of weather on the Adelaide Plains 

 have been so very interesting to the English meteorologist that 

 a few figures will doubtless be acceptable to readers of Nature. 

 On February 18 the shade-maximum temperature at this ob- 

 servatory was 105 '5 during a barometric depression. This was 

 followed by a minimum of 48° 7 accompanying a barometric 

 crest on the morning of the 21st, a range of 568 within thfee 

 days. Again, at 3 p.m. on the i8th the dry bulb read ios°"5, 

 and wet bulb 69°"!, giving the extraordinary difference of 36°'4. 

 These figures actually give 9 as the percentage of relative 

 humidity, according to Guyot. The instruments are exposed 

 in an enlarged Stevenson screen, which answers admir- 

 tbly in this climate ; and what can be a better test ? I 

 may add that I also have a small "Stevenson," of the 

 pattern usually employed in England, with duplicate instru- 

 ments. The differences between the two usually amount to 

 merely a few tenths of a degree. The Hon. Ralph Abercromby, 

 who visited my observatory a short while ago — since my return 

 from Queensland — was much pleased with the result of my com- 

 parison. I reserve a table for the Royal Meteorological Society, 

 but I may mention that I claim to have proved that Mr. 

 Stevenson's screen is in every way suitable for the hot and dry 

 climate of this continent. I am strongly of opinion that this 

 screen, in its enlarged form, should henceforth be universally 

 employed to secure uniformily of exposure — a desideratum of 

 the very highest importance. I have strongly recommended its 

 adoption throughout Queensland. I have found no trace of 

 undue heating of the internal louvres, even under temperatures 

 over ico°. Clement L. Wragge 



Torrens Observatory, near Adelaide, South Australia, 

 March I 



"Radicle" or "Radical" 



May I utter a word of protest against a common, but (as I 

 venture to think) erroneous way of spelling the above word 



