( 538 ) 



NOTE ON CHAPTER VI. 



Standard of Measure, p. 365. 



The inaccuracy to which a standard of measure, derived 

 from the common pendulum, is liable, arises from the diffi- 

 culty of measuring the precise distance between the real point 

 of suspension, and tlie centre of oscillation of the pendulum. 



To obviate this difficulty, Mr. Hatton, and after him, 

 still more successfully, Mr. Whitehurst, devised their im- 

 provements. Since the publication of Mr. Whitehurst, 

 Sir George Shuckburgh Evelyn, assuming his princi- 

 ples, and pursuing his path, has made further experiments, 

 wJiich throw new light on the subject. — See Philos, Trans. 

 1798. p. 174. 



TJ^ie method adopted by the French Institute for obtaining 

 an invariable standard of measure, is to assume a certain por- 

 tion of the whole circumference of the earth. For this pur- 

 pose they actually measured on a great circle of the earth, the 

 distance between Dunkirk and Barcelona, The portion of 

 the meridian from Dunkirk to Rliodes was measured by De- 

 lambre, and that from Rhodes to Barcelona, by Mechain. 

 Fiom tills measurement the length of the whole meridian was 

 easily calculated; after which a ceitain portion of the whole 

 circle (a Jortij-miliionthJ was fixed upon as the standard of 

 measure. This standard the French call the Metre, which is 

 about equal to 39. 371 English inches. 



NOTES ON CHAPTER VIL 



Comparative Dimensions of Ancient and Modern Ships. 

 p. 369. 



V\/ HEN it is asserted that the last age is remarkable for a 

 great increase in the dimensions of ships, it is meant that this 

 may be considered as a general truth. The vessels which, at 



