

ADDENDA ET CORRIGENDA, 



Page 6. The description of 

 7, in the text, is taken from the Memoirs 

 of the Academy of Sciences. It is pro- 

 bable that in the construction of the 

 instrument, Amontons employed a tube 

 of narrow calibre, to enable the included 

 air to support the mercurial column. 

 The proportion between the tube and 

 ball maybe inferred from what is stated 

 of the expansion of the whole, by the 

 heat of boiling water. 



P. 10. In the beginning of the para- 

 graph, just after the first set pf formulae, 

 there is an error which requires correc- 

 tion. Instead o f these formula? applying 

 to all degrees above the freezing point, 

 read, "these formulae apply to all de- 

 grees above the zero of each scale ;" 



P. 14. The notation employed by 

 De Luc requires some explanation. 

 y denotes the height of the barometer 

 in sixteenths of a Parisian line ; T the 

 height of a thermometer, plunged in 

 boiling water, above the melting point 

 of ice, in hundredths of a degree of 

 De Luc's scale ; and a the constant quan- 

 tity 10387, which Horsley thinks, from 

 some of De Luc's experiments, should 

 have been 10369 ; but in his investiga- 

 tions he retains the first number, as 

 probably adopted on good grounds. 



The logarithms used by De Luc are 

 the tables of Briggs, in which the seven 

 figures of the tables, as well as the 

 indices, are reckoned integers ; or he 

 considers the eighth figure in the place 



of units : but it is most convenient to 

 reckon all the figures after the index 

 as decimals, and the formulae will be 



99xlOO r , 



-- Log. y-a=T. , 



P. 15. In the second column of the 

 table, 29. should be opposite to .95, 

 instead of .39. 



The terms lower and higher, in the 

 third column of the same table, are so 

 an the original paper ; but the directions 

 will be more plain, if the reader will re- 

 collect, that where lower is indicated, 

 the correction is " to be subtracted ;" 

 and when higher is used, the correction 

 is "to be added." 



P. 23, Col. 1. The action of the pi- 

 nions in Ferguson's Pyrometer is ill ex- 

 pressed in the text ; and the reader is 

 requested to substitute for the member 

 of the sentence commencing with " and 

 the bar, tyc." in the 14th line, the fol- 

 lowing -"and as the bar k has IrBeen 

 teeth to one inch, it is obvious that 

 when k moves one inch, the pinion I 

 will have made one revolution and a 

 quarter, and the pinion p will have 

 moved 100 x 1|, or 125 times round." 



P. 29. In Wedgwood's table, Col. 1, 

 line 27, for deduct, read, " did not." 



In the same page, Col, 2, the radius 

 of Regnier's instrument should have 

 been -649 millimetres, its diameter 1.298 

 metres, and its circumference 4.079 

 metres. 



