CHANGES IN THE MOON. OBSERVATIONS BY PROFESSOR LAMBERT.

Te Aroha News, Volume VII, Issue 419, 19 October 1889, Page 4

CHANGES IN THE MOON. OBSERVATIONS BY PROFESSOR LAMBERT.

Another change in the moon is reported to have taken place ; I refer to the alleged alteration in the crater Piinius. It will be remembered by many that similar reports have several times come to hand within the last fifty years, and from some of our best observers. The old idea, that it would be possible some day to discover signs of actual life upon our moon, has now bub few supporters, while many of our astronomers cling stronger than ever to the hope of discoveringchange in herinerfc mass. But while this hope issoundandcaptivatingjWhilelrom time to time we may expect to learn of such discoveries, we must not rush hurriedly into bhe belief that they have actually been made when such reports reach us ; for while it is easy to suspect change on a surface like the moon's, while it is scientific to expect such discoveries to be made, we must remember that we are uob looking at an object a few feob away from us, and that things out yonder are not always as they seem. Anyone who has studied the moon's surface from month to month will know well how varied the same object appears under different illumination, and how easy it would be at one time more than another to suspect change here ana there of an actual order. Such observers as Schroeter a:id Gruithuisen, whose accurate observations could hardly be questioned, made this very mistake, as Beer and Maedler pointed out and corrected. In November, 1866, Dr. Schmidt, chief of the Athens Observatory, announced that the crater Linne, situated in the Sea of Serenitz, was missing, and that its place was occupied by a whitish cloud surrounding a most minute crater. This crater was described by earlier observers as at least five miles in diameter, and very deep. After Dr. Schmidt's announcement other observers described it as undergoing change in form and dimensions almost daily, but it is now known that the changes noticed were for the most part due to ihe | varying circumstances of illumination, induced by combinations of libratory effects added to the ordinary changes depending upon the direction of the sun's rays. It would appear, however, that this crater is not actually missing aa Schmidt supposed, but ib is certainly no longer deep. Another change was announced in May 1877 by Dr. Klein. He was observing in the neighbourhood of the well-known crater Hyginus, near the middle of the visible halt of the moon, when he observed a small crater full of shadow, apparently about three miles in diameter. He had frequently observed this same region during preceeding years, and felt certain that no such crater existed in 1876, for it formed so conspicuous an object in the Sea of Vapours that he could not have missed it. The great chart by Beer and Medler which has a diamater of 37 inches and Lohrman's excellent map of 15 inches diameter, were both carefully searched, but no such crater as that announced by Dr. Klein wafe found. It appeared thus far that a new crater had really been discovered in the moon, but subsequent research was destined to throw some considerable doubt upon the matter. The photographs of Rutherfurd, De la Rue, Ellery, and Draper of our satellite taken prior to 1577 were examined ; and as these show objects le?s than two miles in diameter, they were reasonably expected to give very decisive evidence on this interesting subjpct. After every care had been taken in the examination of theso photographs, the result was that no such crater as that described by Dr. Klein wa3 found in any of them. But; in a splendid photograph by E-uther-furd, on March 6th, 1865, the place of Dr. Klein's crater is occupied by a small spot, brighter than the Sea of Vapours in which ib stands. Now, this is the usual appearance of a small crater under a high sun, but whereas no such crater is shown on the later photographs, bub is revealed by one taken twelve years prior to the announcement of its discovery by Dr. Klein, some considerable degree of doubt is thus thrown upon the suggestion that any recent change has taken place in that particular locality. While, therefore, ib is so easy for our best observers to misinterpret what they see upon our moon ; while it is so difficult to interpret aright what is seen owing to the many difficuiies by which bhe subject is surrounded, the reported change in Piinius should be accepted with strong probability only, until careful observation has been made under every possible illumination. But while I have endeavoured to &how bhab bhe alleged changes on the moon in the past have scarcely been proved, I am nob tor a mornenb contending that the moon has assumed her final condition, (that is, that she has attained to such a condition when no further change is possible.) On the other hand, there is no member of the Solar System perhaps, so likely to undergo change as our moon. Nor is it necessary to seek an explanation in scarcely any change the moon can now undergo in the theory ot volcanic forces. Anyone who studies Mr Mallet's admirable theory of volcanic energy will, I think, be convinced that however well it applies to our earth, that it finds as good, it not a better interprebation in bhe presenb condibion of our satellite. It seems to me that if evidence of continued volcanic action is to be sought in the moon, the place to look for it is around the circumference of the disc, •where eruption from any marginal orifice would manifest itself in the form of a protruding haziness, as Nasmyth long ago pointed out ; but such an appearance has never, to my knowledge, been detected. If we want a cause for the change we may expect upon bhe moon's surface, we shall find onesufficiently adequabe in bhe violent alternations of temperature to which that surface is exposed duiing a lunar day and night. For fully 300 hours we know the sun pouis down upon the lunar surface his heat, uninberrrupted by cloud, and untempered by any atmosphere, until her surface becomes heated to a degree which is estimated at 500 degrees FahreDheib, the fusing point of tin or bismuth. Then during her long night of corresponding length, this heat is entirely radiated away until her em face cools down again to a temperature which has been calculated to be 250 degrees below the zero of Fahrenheit's scale. These figures are the results of very careful experimental investigation by Lord Rosse with his six feet reflector, and have since been confirmed by the French observer, Marie Davy. It seems to me that such a severe monthly range of heat and cold as i 750 degrees Fahrenheit cannot but produce very material and telling effects upon ; some, at least, of the component materials of the moon J3J 3 surface, and that sooner or later i some of the familiar details of her surface 1 must undergo more or less change. If '; careful observation should, in the course of < time, prove that changes have taken place i in the crater Pliniue, there seems to me no < reason why we should nob find a clear and i adequate cause for such in the conditions i we have just considered, for it is perfectly clear that such extremes of temperature, i conducted in such rapid succession, and through such long ages, muse disintegrate i some parts of the surface at least, and in i ■time modify the selenographic contour. i

Against this view ib has been urged that the moon's surface matter is composed chiefly of crystalline and porous lavas, which would be likely to withstand the fierce extremes of temperature, thus reducing the probability ot change through the cause we have been considering to ' a minimum. But whatever force there may be in this argument, whatever may be the molecular structure of that face of the moon we see, it is obvious, I think, that where material is heaped in detached masses as we see it on the' moon, that there will be a grating and fracturing of such masses against each other through the alternate expansions and contractions of the entire crust, and that eventually these detached masses will be dislodged and fall to the lower levels. In this way lunai* craters may be wholly or partially filled up, their interiors become modified, and the whole lunar landscape become gradually changed. S. J. Lambert.