308 Intelligence and MUccllaneous Articles. 



vessel round the world witli less than one mile error in longitude at 

 the close of such voyage The errors in their rates were 



Mr. Cotterell's 0-70 



Mr. C. Frodsham's . . 0-86 



Mr. Webster's 0-89 



leaving a difference in the whole year, between the first and last, of 

 nineteen hundredths of a second. To prove the accuracy and at- 

 tention of the gentlemen of the Royal Observatory ; — a question 

 having arisen as to the justness of awarding one of the prizes, the 

 sum of tlie year's errors was revised, and the result was a difference 

 of 066 decimal, or sixty-six thousandths of a second in the year's 

 calculation ; determining the prize to Mr. Webster, as proposed in 

 the first instance. 



We subjoin the performance of the chronometers for the last 

 eight years' trials: — 



1823. First Prize 11-29 



Second ditto 12-87 



1824. First ditto 4-44' 



Second ditto 6-84- 



1825. First ditto 5-44< 



Second ditto 6- 12 



1826. First ditto 2-62 



Second ditto 3 46 



1827. First ditto 4-68 



Second ditto 5'65 



1828. First ditto 4-41 



Second ditto 4*.92 



1829. First ditto 2-27 



Second ditto 3-80 



Third ditto 4-00 



1830. First ditto 3-59 



Second ditto 4-04 



Third ditto 4-34 



ON THE "double WATEU-SCREW " OF THE "CENTURY OF 

 INVENTIONS." 

 To the Editors of the Philosophical Magazine and Annals. 

 Gentlemen, Jan. 23, 18;3!i;. 



The Marquis of Worcester's Century of Inventions has peculiar 

 interest, especially to Englishmen. I will not, therefore, make any 

 apology for offering you an explanation of one of them. 



No. LV. — "A double water-screw; the innermost to mount the 

 water, and the outermost for it to descend more in number of threads, 

 and consequently in quantity of water, though much shorter than the 

 innermost screw, by which the water ascendeth, — a most extraordinary 

 help for the turning of the screw to make the water rise." 



Upon this, Mr. Partington (in his edition of the work) has the 

 following note : — " This appears oneof those extraordinary sleight-of- 

 hand 



