ru 



MOON. 



MOON, SUPERSTITIONS RESPECTING THE. tU 



ia UM horizon, and disappear when they are 90* from that boundary, 

 or when the sun U overhead. We copy from Bohroeter'* ' Seleno- 

 snte' two representation* of the tpc4 Archimedes, 



. 



whn <nrj near the dusk part, the noond when t*t from it 



By the twin of tbee *hao*ow, a* well by oilier mewu, the heights of 

 many of the luniu- mountain* hare been measured, and some hare been 

 found whon height* exceed a mile and it half. 



From the manner la which the moon a Men, as well a* from the 

 tan, whefl abe approaches near them, undergoing no refraction what- 

 ever, it in certain that ahe has either no atmosphere, or one of a degree 

 of tenuity which must exceed, perhape, that of the best exhausted 

 receiver. From this it has been inferred that there are no fluids at 

 the surface of the moon, since, if there were, an atmosphere must be 

 formed by evaporation. It is however enough to say that the fluid", if 

 such then be, must be very different from those which abound at the 

 surface of UM earth. Since the moon has a day (with reference to the 

 sun) of a whole sidereal month in duration, each part is 14} days In sun- 

 light, and 14| days without it. The intense heat and cold which must 

 thus alternate would destroy human life, even on the supposition that 

 terrestrial vegetation could be maintained. The fluid on the warm 

 side i if any) must be constantly evaporating and passing off to the 

 colder aide. " The consequence must be absolute aridity below the 

 vertical nun, constant accretion of hoar frost in the opposite region, 

 and perhaps a narrow lone of running water at the borders M the 

 enlightened hemisphere. It is possible, then, that evaporation on the 

 one hand, and condensation on the other, may, to a certain extent, 

 penerve an equilibrium of temperature, and mitigate the extreme 

 severity of both climate*." (Sir J. Herschel, Astronomy,' p. 230.) 



The man of the moon, as determined from her effect upon the 

 earth's motion, is about one-eightieth (or '012.VJ) of th.it of the earth, 

 her volume is one forty-ninth of that of the faith, and the average 

 density of her material -018, or about six-tenths, of that of the earth. 

 A body weighing six pound* at the earth, would weigh one pound at 

 the moon, u tried against weights which retained their t. ! 

 gravity. Travelling 10 miles an hour on the surface of the moon would 

 enable a person to keep up with the sun ; so that it is not at all im- 

 possible that animal life m.iy be maintained by constant migration, 

 keeping always near the boundary of light and darkness. 



It might be supposed that nothing could ever be known of the figure 

 of the moon, inoe we can only see one side. But this very 

 stance Ir:uk us to some knowledge on the point. It is impossible to 

 believe thnt the moon should revolve on her axis precisely in the same 

 average time a* she revolve* round the earth, without half a second of 

 difference, and not to suppose that there is some mechanical connec- 

 ts m Iwtween the two revolutions, so that either one is a com- 

 of the other, or both are consequence* of Rome common cause. As this 

 subject u rarely elucidated In elementary treatises, we have somewhat 

 abridged sroral of thine topic* which are usually treated, In order to 

 supply considerations for wl,i,-h we ouuld only refer to treatises of the 

 mot mathematical character. 



U U well known in mechanics that the rotation of a body is in n 

 way affected, if we suppose its centre of gravity to be fixed instead of 

 moveable, provided the same forces act In both rases. Thug if a stick 

 be tossed into the air (or rather into vacuum) by an impulse comum 

 nicatod t<> a similar stick which revolves on it* centre of gravity, the 

 first in its combined rotation and translation, and the second 'in iu 

 rotation only, will always remain parallel to each other, if they were 

 so at first: Let us now suppose a needle placed on a point, and mag- 

 netic, round which a ball of iron revolves from A. If the needle be 



D 



o 



in* at rat, then wben the ball move* toward* B, It will endeavour to 

 draw the needle toward* the poiiitta o n, and the neeillc will begin to 

 nrvol e in the mm* direction a* the ball. Suppose that by th* time 

 the needle point, to o n, the ball U at o , oo and on being perpen 

 dkmlar ; th* ball then aeta equally on both aide* of the needS, *nd al 

 BiahinMim of the rotation stop.. When the ball arrive* at D, it Is 



tending to destroy it* former effect, pulling tb* end p towards it. It 

 may thus he seen that if the needle were heavy enough, the ball 

 would by it* motion cause an oscillation, working to produce rotation 

 n one direction during half iU revolution, or rather more, and the 

 opposite effect during rather more than another half revolution, in 

 alternate quarter*. Hut if the needle were light enough, it is easily 

 wen that the rotation in the first direction might be produced so 

 rapidly, that the second mode of action ahould never be exerted, or tho 

 revolving ball should never *o far outstrip the needle that ROC should 

 become a right angle. In this case the action would go on in one 

 direction until the needle Would acquire a rotation equal to and even 

 exceeding that of the ball. But In the latter case, when the needle 

 overtakes and peaces the ball, the opposite action would be immediately 

 exerted, and the acceleration of rotation would b checked. The end 

 would be, that the needle would acquire a rotation equal to that of 

 the ball, on the average, and would revolve so a* always to present iU 

 point either to the ball, or alternately a little on one side and on the 

 other. The same effect would be produced if the needle, at t!.. 

 menoement, had a rotation nearly equal to that of the ball ; tl> 

 eqiicnce would be, that the action in one direction would continue 

 ,<>ng enough to establish permanent equality of the average rot . 

 Without supposing the moon a long needle, with one end turned 

 Lowarda the earth, it is found by calculation, that it is sufficient to 

 suppose it slightly spheroidal, with the longer axis towards the earth. 

 The same mathematical considerations which have so coi 

 solved the orbital motions, show that the figure of the moon must be 

 an ellipsoid [SCHPACKS or THE SKCOSD DEUKKK] revolving round the 

 shorter axis, and presenting the extremity of the longer axis to the 

 earth. But the proportion of these axes have not been well . 

 mined, from want of observation* : thuoiy has outrun practice on this 

 point. It is but comparatively lately that even the inclination , .;' tho 

 moon's equator to the ecliptic has been determined at 1" 'M' 10"'8; 

 that of the equator to the orbit being 6 8' 49", as already noti 



One more very curio; i non has been shown to be of 1 1n- 



same kind as the preceding; namely, of the sort which must be 

 made absolutely true by the earth's attraction, if it were nearly true at 

 the beginning. The moon's equator cuts her orbit in a lincwl. 

 always parallel, or very nearly so, to the mean position, for th 

 being, of the line of nodes of the moon's orbit. If the axis of the 

 moon's rotation were perpendicular to the ecliptic, this muHt 

 case, for the moon's equator and tho ecliptic would then be parallel 

 planes. And the moon's axis lieing nearly perpendicular to the elliptic, 

 it may be shown from spherical trigonometry that the two lr 

 question could not make an angle of many degree*. But th 

 observed (by Dominic Cassini, before the theory of gravitation was 

 thought of) is cither actual |ur.illelism, or something . : oiu it 



by very trivial oscillations. It is difficult to represent this phem , 

 to a person unacquainted with geometry. It may be thus stated : tho 

 moon's orbit, the ecliptic, and the moon's equator, are three planes 

 which fo'm a triangular prism when produced. Or thus : if the moon 

 were made to revolve rapidly round it axis, and if the eartl 

 a source of light and heat giving seasons to the moon, as the BUI 

 to the earth, then the nodes of tin' moon's otliit on the ecliptic would 

 coincide with the equinoxes, and the mixin's orbit would lie .i 

 into summer and winter path* by the same line as that in which the 

 sun'a path cuts the orbit. 



A great many niisccllnnrnu* phenomena connected with the moon 

 might be collected, for which we have not space. For the light thrown 

 on her surface when eclipsed see RKFRACTION ; for a remarkable a 

 ance sometimes observed when she passes over a star see OCCL I.TATIOX ; 

 for her use in finding LONIIITTDK see that word. 

 M<tN. KCI.II'SK OKTHK. [M....X.] 



MI ION. sri'KKsTlTIoNs i;i-:-;i'KOTING THE. Brand, in 

 his ' 1'opulnr Antiquities,' gives a long list of lunar SP 

 It was formerly conceived that if hog* were killed when th, 

 was increasing, the bacon would prove the better in l>oiling. (See 

 the Huabanaman'i Prattitt, or Proynottieation for A'wr, 8vo., 

 I.' md . 1664.) 



Tusser, in his ' Fire Hundred Points of Husbandry,' under 

 February, says : 



" Sowc potuon and beans In the wane of the moon, 

 \\lin Miwi-th tin-ill Homier, lie Hnweth too toon ; 

 Tint tin'}- with the plunrt may rest and rle, 

 And flourish with bearing mot plentiful wise." 



In Decker's ' Match me in London,' act i., the king says, " My lord. 

 doe you see this change i' th' inoone 1 Sharp homes do threaten windy 

 weather." 



Werenfels, in his ' Dissertation upon Superstition ' (Transl., 8vo., 

 I, "lid.. I7IM, p. ti, speaking of a su|KTstitious man, says, " He will not 

 commit hi* seed to the earth when the soil, but when tli. 

 requires it. He will have hi* hair rut when the moon in cither In 

 that bis locks may stare liko the lion's shag; or in Aries, tha: 

 may curl like a ram'* horn. Whatever he would have to grow, he seta 

 it when she is in her increase ; but for what he would have made 

 leas, he chuse* her wane. When the moon i* in Taurus, he never e.iu 

 be persuaded to take physic, lest that animal, which chews it* cud, 

 should make him cast it up again. If at any time he has a mind to be 



