July, 1902.] 



KNOWLEDGE, 



151 



and the leg seems to end with the til>i;i, ou which, of 

 course, the insect walks. 



One of the strangest and most unexpected of the uses 

 to whiih we could iniagiue a leg as beiui,' put is that of an 

 organ of hearing. Yet such seems to be one at least of 

 the functions of the fore-legs in the cricket and some 

 other allied insects. On the outer side of the tibia (Fig. 5) 



Fio. 5. — Fore-tibia of House 

 Cricket, a, auditory organ. 



Fk;. 6. — Fore-leg of Tortoise- 

 shell liutterlly. /, femur; ?, tibia; 

 «. tarsus. 



a small oval space may be seen in which the strong 

 arnuiture which covers the rest of the body is reduced to a 

 thin and membranous condition, making thus a sort of 

 window or drumhead. Communicating witii this, inside 

 the leg. are the ends of a nerve, .ind it can hardly be 

 doubted therefore that the whole apparatus constitutes an 

 auditory organ, so that if these legs were amputated, the 

 insect would become deaf. Wlien one remembers that 

 crickets .are amongst the noisiest of insects, their incessant 

 chirrup l)eing a most shrill and penetrating sound, it 

 cannot be considered strange that distinct organs of 

 hearing should also be present ; the sound-producer 

 implies the soimd-perceiver ; the two functions are com- 

 plementary ; but still it is remarkable that the fore-leg 

 should have Ix-en selected as the most suitable site for 

 this important sense. 



Our last type of leg scarcely deserves the name of leg 

 at all, as it is shrunken in size, and does not reach the 

 ground. It is met with in certain butterflies, which, so 

 far as walking is concerned, move about on four legs only 

 instead of the usual six. The Common Tortoiseshell 

 Butterfly will serve very well to illustrate this peculiarity. 



Here the fore-legs (Fig. 6) are much shorter than the 

 other two pairs, though composed of the usual jiarts. 

 Their whole surface is thickly covered with long hairs 

 which project beyond the end of the foot, and thus 

 effectually prevent it from being used to rest upon, and 

 the whole limb has the ajipearance of a sort of dusting 

 brush. These small brush-like legs lie folded up ou the 

 breast, and their hairiness so effectually conceals their 

 form that they are with difficulty distinguished from the 

 general fluffiness by which they are surrounded ; hence at 

 first sight the butterfly apjjcars to be really a four-legged 

 insect, and it is only on poking abtmt carefully amongst 

 the hairy mass that the apparently missing pair are 

 discovered. 



A NEW ALGOL VARIABLE. +43 4101. 



A STRIKING illustration of the value of the lil)rary of glass 

 photogia|ihs collectt'd at this Observatory during' the past 

 seventeen years has been shown within the last few davs. 

 Comet 1!102a was discovered by Mr. Brooks on April 14th. 

 and It was found that a photO'.rraph had l>een taken here 

 on April 3rd with the 8-inch Draper telescope, approxi- 

 mately in the direction from which the comet came. An 



examination of this plate was accordingly made by Mrs. 

 Fleming, superposing it upon another plate of the same 

 region taken with the same instrument on March 7th, 

 lOuO. No trace of the comet was found, ami in fact the 

 elements now indicate that it was a little beyond the 

 region covered by the photograph. One star, however, in 

 tlie constellation Lacerta, according to Heis. but in Cygnus 

 according to the Uranometria Nova, appeared faint on the 

 early plate and bright on that taken later. A further 

 (wamination showed that this object was the north pre- 

 ceding component of +43'^ 4101. Its position for 1900 

 is E.A. = 21h. 5.5-2m., Dec. = +43° 52'. The dift'erence 

 in right ascension of the two components is about 20s., 

 the difference in declination 0''3. A further examination 

 showed that the star was generally bright and constant in 

 light, so that it must be a variable of the Algol type. It 

 is not very distant from the remarkable variable star 

 SS Cygui, which precedes it 16m., and is 44' south. This 

 last star was discovered at this observatory in 1896, and is 

 ordinarily faint^ becoming suddenly bright at intervals 

 which appear to be irregular. Only one other star, 

 U Geminorum, is known to undergo similar changes. 

 The star, SS Cygni, has l>een carefully studied here, several 

 hundred i)hotographs having been taken of it. It has 

 also been observed visually on several hundred nights 

 both here and elsewhere, but as yet the law regulating its 

 outbursts of light has not been discovered. Again the 

 advantage of the photographic method is indicated, since 

 each plate taken for SS Cygui can be used for studying 

 the new variable, or any others that may be discovered in 

 this part of the sky, as well as if taken for each alone, 

 while of course the visual observations of SS Cygni can 

 be used for no other star. The total number of plates 

 showing the new variable at full brightness is 388, of 

 which 1 was taken in 1889, 10 in 1890, 12 in 1891, 8 in 

 1892, 9 in 1893, 3 in 1894, 10 in 189-5, 37 in 1896, 184 in 

 1897, 30 in 1898, 37 in 1899, 28 in 1900, 7 in 1901, and 12 

 in 1902. Besides these, the star appears on 54 photo- 

 graphs taken with the 25 inch anastigmat, but they have 

 not been included in the present discussion, since the 

 proximity of the other component in some cases renders it 

 difficult to decide whether the variable is at its full 

 brightness or not. Besides these plates, 19 were found on 

 which the variable, which ordinarily has the magnitude 

 8-9, was of the magnitude 93 or fainter. 



At first the jieriod was thought to be l'498d., but this 

 was found to be an error. The true period appears to be 

 about 31o04d., and the times of minimum are represented 

 by the formula, 2,410,01505 + 31304 E. The star 

 retains its full brightness for 28 days, its photographic 

 magnitude at maximum being 8'9. About a day before 

 the minimum it begins to diminish, attaining the magni- 

 tude 90 at I05d. before minimum, 95 at 94d., 100 at 

 S4d., lOo at 0-71d., 110 at 0-58d., and 11 5 at 43. The 

 light remains nearly constant for more than half a day, 

 with the minimum magnitude 116. The time of increase 

 is more uncertain, but apparently is nearly the same as 

 that of decrease. The period of this Algol star, 31 4 days, 

 is more than three times that of any other as yet discovered, 

 and the duration of minimum, 2 days, is double that of 

 S Cancri, the next in length. The period of S Cancri is 

 9'5 days', and the duraiiou of minimum 0'9 d.ay. The 

 last minimum of 4 43° 4101 occurred on A]iril 28th, 

 19112, at 21h. 33m, G.M.T. The predicted times of the 

 next minima .are Mav 30d., 4h. 51m., June 30d., 12h. 8m., 

 July 31d., 19h. 2t-m., September Id., 2h. 44m., and 



October 2d., lOh. 2m., 1902. ^, p, „ 



Edward C. Pickering. 



Harvard College Observatory, 



Mav 6th, 1902. 



