88 Dr. Wrightson on the Atomic Weight and 



equations represent the observations of M. Jamin equally well 

 as the equations given by M. Cauchy, it becomes interesting to 

 inquire into the reason of this agreement. 



The principles from which Mr. Green and M. Cauchy set out 

 are the same; viz. 1st, the equivalence of vibrations; 2nd, the 

 continuity of movement, or equality of coefficients of Lagrange's 

 function for the two bodies ; 3rd, the evanescence of the normal 

 waves. It is plain that the third of these conditions may be 

 introduced into the equations which express the first two in many 

 different ways, by selecting different particular integrals for the 

 equations of motion. Mr. Green has selected one method and 

 M. Cauchy another; they have arrived at formulae differing in 

 form, but equally well representing the observations. This 

 agreement gives a high degree of probability to the common 

 principles from which both geometers have started ; while at the 

 same time the difference in the form of the results must render 

 us cautious in pronouncing positively in favour of either. 



I would venture to propose equations (14) and (16) as empi- 

 rical formulse to represent the laws of reflexion of plane polarized 

 light at the surface of uncrystalline transparent bodies; they 

 admit of easy calculation and comparison with experiment, and 

 may be used provisionally until better can be deduced from 

 theory. Of this, however, I confess I have little hope, so long 

 as the molecular conditions to be fulfilled at the bounding sur- 

 face of two bodies remain to be supplied by our conjectures, and 

 cannot be obtained by direct experiment. 



Trinity College, Dublin, 

 June 20, 1853. 



XI. On the Atomic Weight and Constitution of the Alcohols. 

 By Francis Wrightson, Ph.D.* 



THAT class of bodies which in organic chemistry we under- 

 stand under the term alcohols, and especially that termed 

 sethyle-alcohol, which may serve as the type of the whole class, 

 has ever been an object of particular attention to the chemist. 

 Although, however, the latter is among the easiest of all organic 

 compounds to prepare and to analyse, and notwithstanding both 

 its formation and its numerous metamorphoses under various 

 reagents have been very carefully studied, nevertheless the views 

 of chemists differ widely both as to its rational constitution and 

 its atomic weight. 



Since Berzelius exchanged his earlier view of alcohol, consi- 

 dering it namely as C 2 II 3 0, that is, the oxide of the compound 

 * Communicated by the Author. 



