May 1, 1891.] 



KNOWLEDGE 



85 



of special sense, are distributed at this spot, and the 

 action of the complex apparatus seems to be such that 

 the membranous disc, vibrating in response to the chirping 

 of some distant mdividual, communicates its motion to 

 the air within the breathing-tube, which in its turn 

 affects the neighbouring nerves, thus enabling the insect 

 to perceive the sound. 



Projecting from the hinder part of the female's body 

 is a long ovipositor, consisting of a double boring im- 

 plement, used in depositing the eggs in suitable situa- 

 tions. Large numbers of eggs are laid, and the course of 

 development is similar to that of the cockroach or bed- 

 bug, the eggs yielding small, active, six-legged creatures, 

 something like their parents in form ; after a series of 

 moults, these attain by progressive changes, but without 

 any pause in their activity or suspension of their fimc- 

 tions, the adult size and form, acquiring wings only at 

 the last moult. The metamorphosis is thus incomplete. 



Two long, unjointed, tapering appendages, pointing back- 

 wards, project from near the extremity of the abdomen in 

 both sexes. They are furnished abundantly with very 

 fine hairs, and are probably sense organs, possibly giving 

 notice of impending danger from behind. 



Crickets are pugnacious insects amongst their own kind ; 

 notwithstanding similarity of habits, however, they are 

 often found inhaliiting the same houses as cockroaches. 

 But it seems probable that the steadily advancing armies 

 of the latter insect will, in the course of time, either 

 exterminate them, or compel them to take to an out-door 

 life. This latter they are not averse to doing in the 

 sunnner time even now. But from the way in which they 

 hug the kitchen ;iire, it seems as if artificial warmth is 

 essential for them in the winter. 



CLUSTERING STARS AND STAR-STREAMS. 



By .J. E. Gore, F.K.A.S. 



THE general tendency of the stars to gather into 

 groups, more or less marked, is perhaps indicated 

 by their ancient division into constellation figures. 

 In the Northern Hemisphere we have the well- 

 known groups of the " Plough " (Ursa Major), " Cas- 

 siopeia's Chair," the " Sickle " in Loo, Corona Borealis or 

 the Northern Crown, and Orion ; and in the southern 

 hemisphere the Southern Cross, Scorpion, Corvus, &c. 

 The " Dolphin's Rhomb," the head of Hydra, and the 

 group near the binary star 70 Ophiuchi also form ex- 

 amples of this clustering tendency. 



That in some of these groups, at least, the connection 

 is real and not merely apparent is shown by the com- 

 munity of " proper motions " discovered by the late Mr. 

 Proctor in the five stars of the " Plough," /?, y, S, e, 

 and ^''' — a connection afterwards verified by Dr. Huggins's 

 spectroscopic observation of their motion in the line of 

 sight. We have a similar case in " Cassiopeia's Chair," 

 where several of the stars in this well-known group 

 seem to be moving in the same general direction through 

 space. 



Among the lucid stars, the most remarkable examples 

 of this clustering tendency are found in the smaller 

 groups, such as the Hyades and Pleiades. In the latter 

 cluster — perhaps the most remarkable group of stars in 



* Dr. Auwer's subsequent determinations have, however, shown 

 that in throo of those stars, p, y, and o, the " proper motion " is 

 small ami doubtful. We have, however, a i|uintuple system in €, f, 

 Alcor, and the telusuupic and spectroaoopic eumpuuious uf ^. 



the heavens — six stars are visible to ordinary eye-sight, 

 but some persons gifted with keener vision can see a 

 larger number.* There is a tradition that seven stars were 

 originally visible to average eyes, but that one disappeared 

 at the capture of Troy. With reference to this supposed 

 disappearance of the "lost Pleiad," Professor Pickering 

 has recently discovered that the spectrum of Pleione 

 (which forms a wide pair with Atlas) bears a striking re- 

 semblance to that of P. (34) Cygni, the so-called " tem- 

 porary star of 1600." The similarity of the spectra 

 shown by these two stars suggests that Pleione may — like 

 the star m Cygnus — be subject to occasional accessions of 

 light, which may, perhaps, account for its possible visi- 

 bility to the naked eye in ancient times. Examined with 

 a telescope the Pleiades show an enormously increased 

 number of stars — even with an opera-glass a considerable 

 number may be seen — and in a photograph of the group, 

 taken at the Paris Observatory with an exposure of three 

 hours, no less than 2,326 stars can readily be counted in 

 a space of about 3 square degrees. In this remarkable 

 picture, smaller aggregations of stars are \'isible ; for 

 instance, Alcyone, the brightest of the whole group, forms 

 one of a small cluster of some ten stars, and Maia and 

 Merope have several faint stars near them. A common 

 proper motion in many of the brighter stars'of the Pleiades 

 shows that here also we have a family of stars traveUiug 

 through space together. 



The Hyades also form a remarkable naked-eye group, 

 with the brilliant red star, Aldebaran, as their leader, but 

 the component stars are not so closely crowded as in the 

 Pleiades group. I am not aware whether the Hyades have 

 yet been photographed. 



Another well-known cluster is the Priesepe, or the 

 "Beehive," in Cancer. The stars composing it are, how- 

 ever, scarcely perceptible to the unaided eye, and in 

 ancient times this|cluster, from its nebulous aspect, was pro- 

 bably ranked as a nebula, and perhaps placed in the same 

 class with the great nebula in Andromeda, which was 

 also known to the earlier astronomers. 



Coma Berenices is another example of a scattered cluster. 

 Here the stars are brighter, and may be well seen with an 

 opera-glass. 



Among clusters a little beyond the hmits of naked-eye 

 vision, there are many interesting examples of star clus- 

 tering which may be seen with a binocular or good opera- 

 glass. One of the most remarkable of these surrounds 

 the star 5 Vulpeculie. I give 

 two drawings of this curious 

 little asterism, one (Fig. 1) as 

 seen by myself with a 2-inch 

 telescope, and the other (Fig. 

 2) as drawn by Mr. Espin, with 

 a reflecting telescope of 17:^ 

 inches aperture. The tendency 

 of the brighter stars to run in 

 lines will be noticed, and the 

 curious grouping of fainter stars towards the left of the 

 larger diagram is also remarkable. This group should be 

 photographed. It is surroimded by Milky Way light, 

 accordmg to both Boeddicker and Heis. 



About 2j degrees preceding the bright star Pollux I 

 see a small cluster of stars, of about the 7th and 8tb 

 magnitudes, which, with a binocular field-glass, very 

 much resembles the Pleiades as seen with the naked eye. 

 The stars 10, 11 and 12 Geminorum (north preceding /x 



* Miss Airy is said to have seen 12, and Mostlin (according to 

 Kepler) no loss than 14, 



