On the Moon's Influence on the Atmofphere, &c. I49 



Thus we find that carbon hardens iron till it arrives at the 

 higher pitch of denfity, which is indicated by the metal 

 lofmg grain, and afluming a cryrtallized filvery fracture. At 

 this point ur maximum we may conceive that the refpe&ive 

 proportions of mixtures are fo nearly balanced that the affi- 

 nity exerted by the iron, is juft fufficient to deoxidate the 

 charcoal, and that hitherto nothing but pure carbon fimilar 

 to the diamond has combined with the iron. If, however, 

 the equilibrium is deftroyed by a larger portion of charcoal, 

 then we find the affinity too weak to deoxidate the whole, 

 and part of it unites in the Itate of an oxide of carbon ; at 

 firft conftituting a mottled fracture, and afterwards, as the 

 dofe is increafed, all thofe deepening blueifh gray fhades pe- 

 culiar to foft call iron. Hence carbon or its oxide again 

 foftens iron. Tt never, however, reftores the properties of 

 forging or of hammering One invariable law, however, is 

 maintained, that the fufibility of iron under every circum- 

 stance and modification is in the ratio of the quantity of car- 

 bon united. 



XXV. Refearches relative to the Moon's Influence on the 

 Atmofphere and on the Variations of the Barometer. By 

 C. Cotte, Member of different Learned Societies*. 



D 



URING forty years ftudy of meteorology I have con- 

 stantly viewed, with a peculiar degree of intereft, the influ- 

 ence of the moon upon our atmofphere. 



The opinion of this influence is founded upon a prejudice 

 fo antient, that I thought it worth while to endeavour, by 

 means of refearches and combinations of facts, eftablifhed 

 on the baiis of obfervations contained in our regifters, to dif- 

 cover, not a complete fyftem, but the proper data to conduct 

 us, by degrees, to the folution of the problem. 



The remits of my endeavours in this way may be perufed, 

 I ft, in my Treatife on Meteorology, publifhed in 1774, 

 p. 186, 302, 317, note; 280, 606: 2dly, in my Memoirs 

 on Meteorology, publifhed in 1788, vol. i. p. 100, &c. 

 vol. ii. p. 80 : 3dly, in the Journal de Phyfiyue 1782, part ii. 

 p. 249; 1786, part i. p. 276; 1792, part ii. p. 272; 1793* 

 part i. p. 279; 1800, part i. p. 358, part ii. p. 337; 1801, 

 part i. p. 338, part ii. p. 221, 409. 



The new refearches which 1 now offer to the public have 

 * From Journal dc Phyfique, &c. torn- liv. Prairial, an. ic. 



L 2 been 



