The Lunar Mare Serenitatis. 295 



outline of its shadow. Of smaller craters there are a good many, 

 and Schr. has delineated some not to be found in B. and M. or 

 Lohrm., reckoning up on one occasion twenty-two, though 

 the plain was not fully illuminated. This might in part be due 

 to the superior light and power of his 13 -ft. reflector, which 

 had an aperture of 9 J inches;* but it needs no great amount 

 of selenographical experience to be aware how little stress can 

 be laid upon such discrepancies. Yet we must not pass over 

 everything of this kind too inconsiderately, or allow ourselves 

 to form a habit of invariably refusing a less plausible explana- 

 tion of unknown phenomena. With this error Schr. was 

 certainly noways chargeable ; on the contrary, we find him 

 constantly deducing conclusions from premises which others 

 might consider inadequate. Thus, on the occasion referred to, 

 he lays much stress upon the circumstance that instead of two 

 whitish heights and a hollow, with a speck like a minute hill in 

 its centre, which he had formerly noted towards the middle of 

 the plain, with his 7-ft. reflector made by Sir W. Herschel, 

 and which he had never subsequently seen with any instru- 

 ment, or under any angle of illumination, during upwards of 

 seven years, he now found two distinct bright small craters : 

 while at the same time he perceived two other small craters, 

 hitherto unknown, in a place where he ought to have noticed 

 them in two observations nearly five years before : he found 

 the place of a little crater, recorded more than seven years 

 before, occupied by a grey spot like a longish low hill ; and in 

 another region could not identify some well-known ridges 

 amidst an aspect of general confusion. From all this he in- 

 ferred of certainty of some variation in the lunar atmosphere, 

 induced by natural or possibly even artificial causes, connected 

 with the agency of living creatures. We may perhaps be dis- 

 inclined to follow his line of argument to its full extent. We 

 may think that he did not always sufficiently bear in mind the 

 spirit of his own important remark, that "the longer and more 

 frequently one and the same small spot is observed, so much 

 the more we discover." We may consider it desirable to wait 

 for a fuller and a more rigidly convassed collection of facts 

 before we attempt to make them the basis' of a generalization. 

 But we should not therefore be acting discreetly in rejecting 

 any result of careful observation, however contrary it may seem 

 to our preconceived opinions ; and the history of science may 

 teach us, that of the two extremes, the visionary is more likely 

 than the sceptic to push forward the boundaries of knowledge. 

 Many of the ridges which intersect the plain, and which 

 Schr. compares to the veins of animal or vegetable substances, 



* Probably of the Calenberg scale, equal to a little more than nine English 

 inches. 



