84 Reniarks on the Depressiivi of 



of its elementary particles ; these day-dreams, as they appear 

 -to Mr. Ivory, are despatched in so summary a way, that no 

 ' room is left for dispute respecting them, under the sweeping 

 operation of the general remark, that, " if the truth is to be 

 told, it may be affirmed, that reckoning back from the present 

 time to the speculations of the Florentine academicians, the 

 formula of Laplace, and the remark of Professor Leslie, re- 

 lating to the lateral force, are the only approaches that have 

 been made to a sound physical account of the phenomena." 



Certainly, the truth is to he told, and the truth only; but 

 upon a question of a physical nature, it may be presumed, that 

 other persons may think their own conjectures as good as 

 Mr. Ivory's ; and since he has not stated any reasons for re- 

 jecting the opinions of his predecessor, it would be useless to 

 enter into any argument on this part of the subject. 



But where a mathematical computation is concerned, Mr. 

 Ivory's authority is far too high to be rejected without exami- 

 nation ; and I had no doubt whatever, at first sight, that his 

 " Table of the depression of mercury in glass tubes," was, as he 

 asserts, so carefully calculated, that all the numbers might " be 

 reckoned exact, with the uncertainty of one unit in the last place 

 of figures," and I copied his numbers at once into the table of 

 the former article, with the impression, that it ought to hide 

 its diminished head before them, taking it for granted, that 

 Mr. Ivory would not have made an assertion so positive, and 

 so derogatory to the labours of another, without having fully 

 assured himself of its perfect accuracy : but a little further 

 examination convinced me, that I had been too much in- 

 fluenced, in this admission, by the authority of a great name, 

 and too much dazzled, by the brilliant display of logarithms and 

 exponentials, exhibited in the article Fluids. 



The general equations employed in both methods are the 

 same ; the quantities derived from experiment are not materially 

 different ; and even the results of the two tables agree within 

 the limits of the errors of observation in single cases ; so that 

 Mr. Ivory will not be disposed to deny, that the series of the 

 article Cohesion is perfectly true, as far as it is sufficiently 



