232 



KNOWLEDGE 



[October. 1901. 



eye-like mark in tbe hind wings. I may be wrong, but 

 I flatter myself that I was the first to discover this 

 variety of lo. I saw no clouded yellows in either clover 

 or lucerne, and although I am told of good takes this 

 year at Sheemess, especially of hyah, the pale species, 

 I think it unlikely wc should have two clouded yellow 

 years in succession. One hairstreak ('/'. qurrcus) about 

 completes my list of rhopalocera. With the sphingidce 

 I had a good time. It was a grand sight to see the 

 huge convolvulus-hawk moths darting round and about 

 the tobacco plants at dusk. Five or six were often there 

 together humming like a hive of bees. They first 

 appcare<l on the 20tli, and kejJt it up all through the 

 month. The females, though decidedly inferior in mark- 

 ings and antennre, were always the largest, measuring 

 some five inches from tip to tip. The specimens I took 

 are so perfect that it is difficult to believe they are not 

 home-bred. So far the moths of this species taken in 

 Great Britain have been considered to be foreign-bred, 

 but I have just examined a live pupa of -S'. convo/vuli, in 

 the possession of Mr. F. W. Frohawk, which is evidently 

 a genuine specimen. The long trunk of the imago is 

 very conspicuous in this pupa. This is, I believe, the first 

 authenticated pupa of the convolvulus-hawk moth taken 

 in Great Britain, though I ha.ve read in the Field 

 and elsewhere of several reported t<ikes of the larvae. 

 As regards the perfect insects we soon ceased 

 taking them, yet they gradually diminished in 

 numbers, and now I hear there are none ; but according 

 to my experience of their habits, they will assemble 

 again at Benacre, in full force, about October. Afropoi 

 (death's head) larvse were brought to me frequently, 

 dug up while pulling potatoes. They are addicted to 

 buiTowing during the day, long before the final burial. 

 Henco should be sought for at night, with a lantern, 

 when they have emerged for a feed. It is curious what a 

 largo air-chamber this caterpillar makes under ground, 

 in which to perform its two great transformations. If 

 they are dug up it is better to force the pupa3 in damp 

 moss, and in a warm room, or othei-wise they rarely 

 sui-vive the winter. I took both lar-va and imago of 

 privet-hawk, also the larva of the eyed-hawk on an old 

 willow. The beautiful little humming-bird moth was 

 decidedly scarce this year, though it is generally a 

 feature in the well-stocked Benacre gardens. Leaving 

 the hawk-moths I come to the handsome tiger, drinker, 

 and oak-egger, all of which my caddies brought me on 

 the Southwold Golf Links. At light I took two species 

 of thorn, viz., canary-shouldered and early. In a cover 

 by the sea I took a perfect specimen of a female black 

 arches, a.sleep on the trunk of a gigantic oak. Some 

 years ago I took a male in the same locality. At sugar, 

 red underwings appeared early, viz., 16th, but were 

 never numerous. My great take was C. frarini (Clifden 

 nonj^areil) on sugar on the 24th August. In my ex- 

 citement in taking it I chipped the tip of the right 

 upper wing. Otherwise it is a perfect specimen of this 

 rare moth. With the lamp turned on, it showed to the 

 full its grand expanse of upjjer, and gorgeous colouring 

 of lower, wings, and it was a sight I shall not easily 

 forget. For toads, hornets and wasps I was fully pre- 

 pared, but a full-fed lai-va of the goat^moth on the 

 sugar seemed to me out of place. Jos. F. Green. 



Blackheath. 



following statement : — " It is generally conceded that 

 tlie spots on the surface of the sun are the result of 

 greater activity in the circulation of the solar atmo- 

 sphere, and therefore indicate greater heat and, there- 

 fore, light. This being so, the curve representing tbe 

 spotted ai-ea may bo regarded as a lights cui^ve of the 

 sun." I thing this statement is not quite correct. 

 Greater heat may not imply more light, above a certain 

 tcmperatiu-e the reverse is the case. Gas in an ordinary 

 jet gives light; in the flame from a Bunsen biumer, or 

 in the cone from a blow-pipe, we have much gieater 

 heat and very little light. The flame of a spirit lamp 

 gives greater heat than a candle, but it gives veiy little 

 light. I think the sentence should read, " greater heat 

 and, therefore, /fss light." Certainly the spots are much 

 darker than the photosphere. Notwithstanding this, 

 the analogy between the two curves may hold good with 

 a different explanation. For similar reasons we need 

 not regard the brightest stai's as the hottest, probably 

 the reverse is the case. A. Elvins. 



Toronto. 



[Mr. Elvins raises questions which would take no 

 small space for their discussion. It may certainly bo 

 granted that the sentence which he has quoted is, when 

 taken by itself as it stands, extremely crude. _ We are 

 not yet in a position to state unfalteringly that the 

 sun gives most light at the sunspot maximum, or that 

 its light varies with the spot curve. On tbe other hand, 

 it is of coiu-se generally true that increase of heat means 

 increase of light, the instances Mr. Elvins mentions 

 notwithstanding. In the case of the sun, and we infer 

 in the case of the stars likewise, the light proceeds for 

 the most part from the photosphere, and this is con- 

 sidered to be a condensation surface. We might con- 

 sider then that an increase of temperature would 

 diminish the amount of condensation and so lessen the 

 amount of light radiated. But it seems more probable 

 that the actual effect would be simply to raise the level 

 at which condensation took place, and therefore to form 

 a greater radiating surface and one less affected by 

 absorption fi-om the sun's immediate surroundings; in 

 other words, we should have an increase in the light. 

 In the case of stars the brightness is obviously no guide 

 to their temperature, since their brightness depends, 

 among other things, on their distance. The relative 

 temperatures of stars are therefore determined by com- 

 paring the intensities of their spectra in the violet and 

 idtra^violet, not by comparing their stellar magnitude. 

 — E. Walter Maunder.] 



SUNSPOTS AND LIGHT. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — In the Pruceedingit of the Royal Society, 

 No. 446, page 295, Dr. W'. J. S. Lockyer makes the 



j^Ot(CC0 of ISoolis. 



" Star Atlas, whh Ivxplanatorv Tt-xt." By Dr. Hermann J. 

 Klein. Translated by Edmund SlcC'lure, M..\., m.e.i.a., f.l.s. 

 (S.P.G.K.) Price lOs. — This excellent atlas of the stars is too 

 « ell known to need extended notice. In the present edition the 

 text has been revised and considerably enlarged, and the 

 positions of the stars have been corrected to 1900. The notation 

 for nebulje now includes that of the New General Catalogue, as 

 well as that of Herschel. For the benefit of readers as yet un- 

 acquainted with the atlas we may add that the maps cover the 

 heavens from the north pole to declination 34 degs. south, and 

 include all stars down to magnitude 6.5, as well as the principal 

 clusters and nebulse, while the text consists of useful notes on the 

 various objects of interest which come witliin tlie range of 

 moderate telescopes. Besides the star maps tliere are a number 

 of views of clusters and nebulfe, but some of these might with 

 advantage have been copied from photographs instead of from old 

 drawings. Wliile regretting that all reference to the Milky Way 

 is omitted, both in maps and text, we cordially recommend the 

 atlas to those desiring a tru.stworthy guide to an intimate 

 acquaintance with the stars. 



