[ ^101 ] 



LXIX. Continuation of the Reply to Mr. Riddle's Remarks on 

 Jlir. Meiklr's Paper ^^ On the Lunar Observations." By 

 Mr. Meikle. 



To ]\lr. Tilloch. 



Sir, — In your last Number I hope I have cleared my paper 

 on the lunar observations from some of the groundless charges 

 of Mr. Riddle. There still, however, remain several other things 

 to be noticed. For the most part Mr. R. has been at great pains 

 to prove trifles which every body knows, and which I never de- 

 nied. But passing over this at present, I come to consider the 

 learned demonstration which he employs to prove that my me- 

 thod of finding the true altitude of the centre is not more accu- 

 rate than that method in which the reduced semidiameter is 

 used*. With regard to this, I need only observe, that if he had 

 given my paper a fair reading, he might have seen ])iainly that 

 it is not the method with the reduced semidiameter " on v,-hich 

 I animadvert with so much severity," (page 35, line 28,) but 

 the common slovenly method almost in universal use, in v*hich 

 the reduction of the semidiameter is not used at all ; and at the 

 altitude of 7° this reduction on a mean amounts to 18", which 

 is just the error complained of. I there called it a needless error, 

 and so I do still ; for the very accurate method which \ recom- 

 mended, is attended with as little labour as the most slovenly me- 

 thod can be. 



Acain: In giving his *' vulgar test of arithmetical computa- 

 tion," he does vcrv unfair to compare niv method with what he 

 calls " the common method." Now, in the common method, as 

 every body knows, the reduction of the semidiameter by refrac- 

 tion is neglected altogether ; and it was for this very neglect that 

 1 " animadverted on it with so much severity." I must how- 

 ever remark, that 1 have never, throughout my whole paper, al- 

 though Mr. Riddle would fain insinuate it, inculcated the ob- 

 servance of such nicetv at sea; where, as is too well known, 

 some seamen are tolerably content if they get the altitude within 

 half a degree of the truth ; and for such, the common method is 

 certaiidy more than sufficiently correct. But still, when at any 

 time persons, who are not aware of its incorrectness, make a 

 landing, and attempt to determine their geographical situation, 

 it must of course be erroneous. It was for this very reason that 

 I so (kservcdly censured the method of finding the latitude by the 

 pole star. In giving an a|)proximation, it is surely the least thing 

 an author can do, to mention that it is not theoretically correct, 



• That the apparent altitude of the cenlre may also be got correctly by 

 this method, is what I never once called in tjueation. 



Vol. 54. No. 2G0. Dfc. 1819. Cc and 



