2U 



KNOV^TLEDGE 



[Aug. 25, 1882. 



Our butterfly caught, killixl in the usual manner, impaled 

 and brought home, all the material being made ready, and 

 the gum dissolved in cold water and strained through a 

 piece of muslin, the operator must take it (holding tightly) 

 by the pin, in the left hand, and with a sharp knife or pair 

 of scissors cut off tlie four wings as closely as possible to 

 the body, letting them drop on a clean sheet of ordinary 

 paper. ' 



The next step is to take the tweezers and arrange the 

 wines with the underside uppermost, and place the tiuubler 

 over tliem to prevent a breatli of air moving them. 



Then take a half-sheet of note-paper and fold it across 

 the middle, and having opened it again, smear it over about 

 half the surface towards the middle of the paper with the 

 gum ; hold it by the edge with the left hand, lingers length- 

 wise, and with the second linger of the right hand distribute 

 the gum over the paper, pushing it from left to right, an<l 

 then turning the paper round and doing the same, until on 

 holding it up and looking at it sideways in the light no 

 lines can be seen. Place the paper breadthwise before you ; 

 and with the tweezers arrange the wings on the nearest 

 half of the gummed paper, placing tirst the upper wings 

 and then the lower wings as they would appear when the 

 insect is " set '' in the usual manner, leaving, however, 

 room for the body, which must be carefully preserved and 

 ticketed in a manner which will show what wings it belongs 

 to. 



Having arranged the wings, which, once placed, must 

 not be again moved under pain of the specimen being 

 spoilt, fold over the paper, l.-t it stick together, and rub 

 hard on the outsides, top and bottom, where the wings are 

 placed, w ith a pocket-handkerchief over the finger. Open 

 tlie paper, remove the wings, which may be done by 

 blowing or lifting them gently and carefully with the 

 tweezers from the end nearest the body, and all the scales 

 will \,e found to have stuck to the paper in order as on the 

 butti-rfly itself, there being an upper and under view. 



After this, the paper must be washed over with clean 

 water, to remove the gum (being careful to go close up to, 

 but not over, the scales), using the blotting paper to absorb 

 it, and, when the surface is quite clean, placed in a heavy 

 book to press and dry. 



When thoroughly dry (in a1x>ut halfan-hour) commence 

 to paint in, with ordinary water-colours, the body, between 

 the wings, to do which well, and get a good copy, will re- 

 quire some practice. 



When this is finished, the paper may be cut in two and 

 stuck into a scrap album with thick cardboard leaves ; the 

 species, upper or under wing, being written in one corner, 

 and the place and date of capture in the other, or as the 

 collector's fancy may dictate. 



Tl>« great utility of this system appears to me to be 

 that «p«icimen8 are freer from any chance of being destroyed 

 by moths or dust when by Occident the necessary supply 

 of camphor is forgotten to be renewed, and a much more 

 portable collection is obtained, which can be laid on the 

 drawing room table, carried aljout, or even dropped, with- 

 out danger to the sp*;cimen8. 



I have transferred to jiap-r in this manner a number of 

 West Indian butterflies caught more than fifty years ago, 

 and given to me in various stages of decay and destruction. 



One fact has Ureri revealed to me by this process wliich 

 I did not know Ufor*-, and that is that most l»utt<frflies and 

 mothx have two w.-tn of fn-ales ami fringe round the borders 

 of the wings. This is proved by the fringe bi-ing perfect 

 on both the upp«T and undf-r vii-w, and by the fact that I 

 Ijave once or twice lK«n able, with great care, to take two 

 impressions from the same wings. 



In every case but one, I have found the above described 



method to be sui-cissful, and that one failure is in tlu- 1 l.n- 

 butterflies, of which the under sides of the scales (which 

 appear iijipermost on the print), are of a whitey-blwi- 

 colour, and not the bright tint which we see so often flitting 

 about our fields. 



I trust that I have made the above fairly plain, thouc'li 

 not so short as 1 or you might have wished ; but ii 

 any of your readers find a ditliculty in carrying out tin' 

 directions, 1 shall be pleased to answer any questions they 

 may like to pvit. The key to the whole filing is the con 

 sistenco of the gum and delicacy of touch. 



HAS THE MOON AN ATMOSPHERE ? 



By Mr. Ranyakd. 



NO lunar clouds are ever seen floating over the 

 sharply-detined objects of the lunar land.scape. As 

 the sun rises upon the moon, the transition from dark- 

 ness to light is quite sudden. No zone of twilight stretch- 

 ing beyond the sun-illuminated region can be detected, 

 and as the moon passes over bright stars, there is no gradual 

 diminution of their li,;,'ht as they approach the lunar limb, 

 but they disappear suddenly, as if snufled out, at 

 the instant that the lunar limb covers them. It is 

 quite certain, therefore, that the moon has not a vapour- 

 laden atmosphere which is as dense, or nearly as 

 dense, as the atmosphere which envelopes the earth. 

 There is no e\idence tending to show that rays of light are 

 bent as they graze the lunar limb. Rays graz ng the earth'* 

 surface in a similar manner would be turned through aa 

 angle of more than a degree from their original course by 

 refraction in the earth's atmosphere, for it is known that 

 stars, when seen upon the horizon, are raised more than 

 half-a-degrco above their true places by the bending which 

 rays of light undergo before they reach the observer. If 

 there were any su3h refraction of light by a lunar atnio- 

 sphere, the sun would never be entirely hidden by the dark 

 body of the moon during an eclipse. During the reccrjt 

 total eclipse, as seen from Sohag, the moon's diamcrter was 

 about half-a-minute of arc greater than the sun's diameter, 

 and at the time of central eclipse, when the centre of the 

 moon's disc coincided with the centre of the sun's disc, the 

 sun's limb would have remained visible if there hod been 

 o lunar atmosphere giving a refraction equal to I-240th 

 part of the refraction which would have been causc^d Ijy 

 the earth's atmosphere. Hut not only was the sun's limb 

 hidden at the time of central eclipse, but it remaineci 

 hidden for more than a minute — in fact, the observed dura- 

 tion of totality agreed within o few seconds with the dura- 

 tion calculat(^d on the supposition that there is no bending 

 of light by o lunar atmosphere. 



There is always some discordance amongst observers ai 

 to th(r actual duration of totality, for the disappearance of 

 the sun's light is not an absolutely instantaneous phenome- 

 non, so that occasionally trained observers standing beside 

 one another ditl'er as much as three or four seconds in their 

 estimates of the, time of the commencement of tli(; total 

 phas<!. There is also some uncertainty as to the real diame- 

 ters of the sun and moon. Hut after making allowance 

 for these uncertainties, we may safely assert that tho 

 observed duration of total eclipses agrees with tho colcu- 

 lat<:d duration sufficiently closely to (jnable us to bo sure 

 that there is not' an atmospliere about the moon capable of 

 causing a refraction equal to one two-thousandth part of 

 the refraction wliioJi would bo caused by the earth's 

 atmosphere under similar circumstances. 



liut this docs not prove that there is no lunar atmo- 

 sphere, or even that there is not a lunar atmosphere equal 



