SIR J. COCKLE ON MATHEMATICAL HISTORY. 11 



paper, I see that Prof. Young, examining for the Andrews 

 Scholarship, 185 1, at University College, London, again 

 noticed (in question 7) the law. 



3. In 'Notes and Queries' (1854, vol. x. p. 48, see 

 also p. 191 ; and 2nd Ser. vol. viii, p. 465, vol. ix. p. 340, 

 vol. X. p. 162; and 4th Ser. vol. ii. p. 316) I long ago 

 pointed out that Barocius, in the margin of p. 264 of his 

 ' Proclus ' (1560), cites the ' Geometricse Enarrationes ' of 

 Geminus, and I suggested that there might yet be some 

 hope of recovering that work. In a comment {ib. 2nd 

 Ser. vol. ix. p. 449) on something I had said, De Mor- 

 gan remarked that he took " enarrationem " as a printer's 

 mistake for " efiFectionem," if Heilbronner were right, 

 adding that, if there be, as both Petavius and Heilbronner 

 seem to state, a printed catalogue of the manuscripts of 

 Barocius, it would be desirable to revive the knowledge of 

 it. De Morgan states that Petavius is the authority for 

 manuscripts of Barocius being brought to England, and 

 that it may be that a manuscript book of Geminus, which 

 Petavius describes as " nondum editus,'' yet exists in some 

 English library. One of two strange things must have 

 happened . (see De Morgan, ib. p. 450): viz. either the 

 minute Petavius omitted the title of the work, if it were 

 given ; or Heilbronner preserved a title from some other 

 source, if it were not. I am not aware that the manuscript 

 has been discovered. 



4. Lagrange, at page 2 of vol. i. of his 'Mecanique 

 Analitique ' (1811), observes that the laws of statics are 

 founded on general principles which may be reduced to 

 three, that of the lever, that of the composition of forces, 

 and that of virtual velocities. He says (i6. p. 18, No. 14) 

 that the principle of the lever is the only one which has 

 the advantage of being founded on the nature of equilibrium 

 considered in itself, and as a state independent of motion. 



