JiNE, 1902.] 



KNOWLEDGE. 



129 



the details of their structure, this curious contrivance 

 occurs in uo other plants, and yet the two orders are 

 as widely separated as it is possible to conceive. The 

 orchids belong to the petaloid division of ^[oiiocotylc- 

 dons; tlic Asclcpias to tlic ganiopetalous Dicotyledons, 

 with their nearest allies among tho Apocynaccre, of which 

 Vinca. tho periwinkle, is perhaps tlic best known rc]ne- 

 sciitative. Although agreeing in this one particular the 

 llowers are in other respects very dissimilar. 



to time as to the condition of the 



I'la. 1 1.— Flonir ol' CoruiK'^ii. ¥ia. 15. — Birtliwort 



and Cufkoo-piiit showing 

 inouse-tnip hairs. 



Another cunlnvanco lor pruuioting cross-fei-tilisalion 

 met with in unallicd plants is the mouse-trap arrange- 

 ment of hairs by means of which small flics arc tem- 

 jjoriu'ily imprisoned. This arrangement occurs in 

 Aristolochia, in species of Arum, and in Ceropegia, one 

 of tho Asclepiads. In these plants where tho affinities 

 are so slight the mechanism for fertilisation must in 

 each case havo arisen independently. 



ASTRONOMY WITHOUT A TELESCOPE. 



By E. Waltek Maunder, f.r.a.s. 

 XIV.— SUNSPOTS AND MOONSPOTS. 

 Theke are only two of the heavenly bodies which present 

 a disc to our ordinai-y sight, and the surfaces of which 

 therefore we can study without a telescope. These are the 

 sun and moon. It is, of course, absolutely impossible that 

 observations thus made can in any way compete with those 

 made even with a hand-telescope; but from the point of view 

 of astronomical drill, as distinguished from actual re- 

 search, there is something to be said for systematic work 

 upon both of them. Jupiter as seen with a magnifying 

 power of 50, Mars at a mean opposition with one of 100, 

 Saturn with a similar magnification, present about the 

 same apparent disc as the sun and moon do to the naked 

 eye. There is therefore a real interest in seeing how 

 much detail the eye can actually detect upon these two 

 bodies. The limit of magnification possible for the 

 efiicieut study of the surfaces of the planets is .soon 

 reached, and when an astronomical artist has done his 

 very best with Ju]iiler, Mars, S.iturn or Venus, it would 

 bean invaluable check upon his work if he wnuld draw 

 the sun or moon with a little inslrumi'Ut, and such small 

 mat,'nidcation as would give to its disc the same apjiarent 

 diameter as had been presented to him by the planet 

 which he had just been studying. The "Bulletin de la 

 Socii'tc Astrouomique i.le France ' for lyOO contains a 

 large number of such drawings of the moon, made with 

 tho naked eye, and the study of them is. I think, most 

 instructive on a number of jioitits which have been in 



dispute from tinit 

 surface of Mars. 



The defining power of the eye is, of course, Inniteil, and 

 when a number of details are presented to it, each one of 

 which is much too small to be dctiucd separately, all together 

 ]iroduce a composite effect to which each detail has con- 

 tributed in its own degree. Now there certainly is a wide 



Phutouranli of Moon, taken 1902, Ma 

 a. M. T. 



22, lOh. 37m. 24s. 



difference in the manner both iu which such composite 

 effects will impress different persons, and iu the way iu 

 which they will record them in a drawing. And the study 

 of the " personality " of astronomical artists should be a 

 necessary precedent of the comparison and collation of 

 theu- drawings. The drawings of the moon, given iu the 

 volume referred to above, are as widely different as any set 

 of drawings that were ever made of Jupiter or Mars. Yet 

 a careful comparison of them with maps or photographs 

 of the moon will show that the forms given are not 

 imaginary, but have a real relation to the lunar markings, 

 whether they be skilfully represented or no. 



The following drawmgs are from the volume cited, 

 pages 277 and 505, and are by M. Maimce Petit and 

 M." E. M. Antouiadi respectively. The latter comments 

 on his observations as follows : — 



" It is a work of immense dillioulty to draw correctly all tin" 

 " details that the naked eye rcveaU to us on the sui-face of our 

 " satellite. It is aliovc all things necessary that the muon slioidd 

 •■ be seen with the greatest [lossiblc distinctness. If the eye is nut 

 ■' oninietropio it will he necessary to select glasses of the proper 

 " focus bringing the focus exactly on the retina. The acconi- 

 •' panjjng sketch which is oidy a rough apjjroximation was obtained 

 " with concave ghisses, allowing at least ten stars to be seen in tho 

 " grou|i of the I'leiadcs ; it is the residt of studies covering several 



'• lunations The darkest spots seemed to nw (1), the Mare 



" Trannuillitatis, and (2) Mave Xubium. Tlie Mare Screnitalis and 

 " Fecunditatis come next. Mare Imbrium and Oceanus Proccl- 

 " laruni are still ])aler. The little .MariaCrisium,Vaporum, Iluniorum 

 " and Nectaris, are reduced iu size liy irradiation, and present to tlic 

 " naked eye an appearance corresponding to that of tlie Lacus Soli- 

 " and Lacus Luuie of Mars as seen in a telescope. The white spol- 

 " of Copernicus and Kepler are very well seen, Ai'istarchus with 

 " more diilicultv, whilst Tycho, with its brilliant surroundings, 

 ■• oivupics an immense white surface ; but .... the ring itself 

 •■ is not -ecu, Gucrike. lionplund. I'arry and Fra Mauro make up 



