392 Scientific .Ivtelftgsifffc [$«?}. 



The words of Dr. Clarke are, " all the railing clouds disap- 

 peared, excepting a belt collected in i'okm Of a ring highly 

 luminous, annuid the moo/);"' evidently implying, not (as A. 

 would have it) that there was the form, or appearance, of a ring 

 around the moon, but that there was a cloud (otherwise I know 

 not the use of the word " excepting ") encircling the moon in the 

 form or shape of a ring-. If X. means to assert that Dr. Clarke 

 "is not a perspicuous writer, the subject is immediately changed ; 

 but I am not of opinion, from the acquaintance that I have with 

 Dr. Clarke's works, that there is room for supposing that he 

 wrote otherwise than he meant. 



AH that I attempted to show in my former letter was, that this 

 appearance could not arise from a cloud situated as above 

 described. 1 will now further observe that it must have been by 

 a most extraordinary coincidence — a coincidence indeed hardly 

 to be believed, thai a cloud lying wholly between the moon and 

 the spectator presented such an appearance as that depicted by 

 Dr. Clarke in p. 488 of his volume. It was on this account that 

 I requested Dr. Clarke, or some other of your intelligent corres- 

 pondents, to suggest some more satisfactory principle on which 

 the phenomenon might be accounted for. I have failed to obtain. 

 *ueh information as 1 desired ; for the Doctor himself seems to 

 have viewed this appearance of the moon in no other light than 

 as a beautiful spectacle, or, perhaps, as it might make a figure in 

 "his quarto ; and as to any other quarter from which information 

 may be derived, it is hardly to be expected that any person 

 should set about explaining what he never saw. It appears then 

 upon the whole that I must be content to believe that such a 

 phenomenon was once seen, but from what cause remains, and 

 is likely to remain, one of the unfathomable secrets of nature. 



I cannot conclude these the last remarks I shall make on this 

 question, without observing, that although I am now no more 

 enlightened on the subject than at the date of my last letter, still 

 the desire of obtaining information, by whomsoever expressed, 

 on subjects which excite the doubts of the inquirer, can be con- 

 sidered by X. alone as " too ludicrous to merit further notice." 



I am, Sir, your obedient servant, 



S. 



XVIII. Mathematical Problem. By Mr. Adams. 



(To Dr. Thomson.) 

 SIR, Stonchouse, Sept. 4. 1819. 



On reconsidering problem 4, Art. IV, of the Annals of Philo- 

 sophy for March, 1819, I find that a small alteration in the 

 formula there given will reduce the solution of the problem; jta 

 one general rule, the insertion of which, in seme future number 

 of your journal, will much oblige, Sir, 



Your most obedient servant, 



James Auams. 



