270 Mr. Rider's Rotatory Steam-Engine. 



in my humble opinion, bids fair to constitute one of the greatest 

 improvements yet made in the steam-engine. 



I had almost forgotten to mention a circumstance which has, 

 doubtless, operated against the good name of this invention in 

 Glasgow, i. e., the bad success attending the engine put on board 

 the Highland-lad steam-vessel, by Messrs. Girdwood and Co., 

 through Mr. R.'s license. In consequence of the evil reports 

 (which were industriously circulated,) Mr. R. and I went to Glas- 

 gow, where, on inspection, Ave found the engine differed most ma- 

 terially from his plan, and was extremely defective indeed, so much 

 so, that it is wonderful it had any power whatever. By way, how- 

 ever, of letting the good folk on the other side of the water witness 

 the astonishing effect of his improvement, he is now engaged in 

 constructing an engine to be mounted in a boat at Glasgow, where 

 all may have an opportunity of judging for themselves. 

 1 have the honour to be, 

 Sir, 



Your most obedient servant, 

 WILLIAM BOYD. 



Art. IX. Observations on the Modern Theory of Physical 

 Astronomy. By John Walsh, Esq. 

 [Communicated by the Author.] 

 Men, in general, are too apt to form theories without thoroughly 

 examining the bases on which they found them, and the conse- 

 quences that may follow from them ; and, as well as others, the 

 geometer and the natural philosopher have often committed them- 

 selves in this way. When the geometer departs from the spirit of 

 demonstration, he is no longer to be depended upon. Sometimes 

 I meet, even in the works of the most illustrious mathematicians, 

 with the expression, " rigorous demonstration." This sounds 

 oddly , I cannot perceive the necessity of the word rigorous, or 

 of any adjunct of similar meaning, as applyed to demonstration. 

 Both sides of an equation, being only different manners of repre- 



