156 



Dr. Hofmann on MetJiylic Aldehyde. 



[Nov. 21, 



IV. — ^' Second Supplementary Paper on the Calculation of the 



Numerical Value of Euler^s Constant.''^ By William Shanks, 

 Houghton-le-Spring, Durham. Communicated by the Kev. Pro- 

 fessor Price. Received August 29, 1867. (See page 154.) 



V. " Addition to Memoir on the Resultant of a System of Two Equa- 



tions." By A. Cayley. Received August 6, 1867. 

 (Abstract.) 



The elimination tables in the memoir on the Resultant of a System of 

 two Equations (Phil. Trans. 1857, pp. 703-715), relate to equations of the 

 form (a, 6 . . ^it% ?/)™=0, without numerical coefficients; but it is, I 

 think, desirable to give the corresponding tables for equations in the form 

 {ci, 6,.^cr, 2/)™ = 0, with numerical coefficients, which is the standard 

 form in quantics. The transformation can of course be elfected without 

 difficulty, and the results are as here given. It is easy to see d jpriori that 

 the sum of the numerical coefficients in each table ought to vanish ; these 

 sums do in fact vanish, and we have thus a verification as well of the tables 

 of the present addition as of the tables of the original memoir, by means 

 whereof the present tables were calculated. 



VI. " Contributions to the History of Methyhc Aldehyde." By 

 A. W. Hofmann, LL.D., F.R.S. Received September 30, 1867. 



''The aldehyde of the methyl-series is not known ; " all the chemical 

 manuals say so, and for the last twenty years my students have been duly 

 informed thereof. It will scarcely appear strange that more efforts to be- 

 come acquainted with that body should not have been made, since the 

 masterly picture which Liebig has delineated of the aldehyde par excellence 

 embraced as it were the history of the whole class, and of course also of 

 the aldehyde in question. Nevertheless methylic aldehyde deserves our 

 consideration for more than one reason. As one of the simplest terms of 

 the monocarbon-series, occupying a position intermediate between marsh- 

 gas and carbonic acid, as a link of transition coimecting methylic alcohol 

 and formic acid, as either aldehyde or acetone, according to the point of 

 view from which we look upon it, the compound CH^O illustrates a 

 greater variety of relations than any one of the higher aldehydes. But in 

 addition to the interest with which the methyl-compound has thus always 

 been invested, this substance possesses special claims upon our attention at 

 the present moment. Our actual method of treating organic chemistry for 

 the purposes of instruction almost involves the necessity of starting from 

 the methyl-series. The simplest of aldehydes thus acquires quite an espe- 

 cial importance, and all those who, like the author of this note, are engaged 

 in teaching, cannot fail to have sadly missed a compound which is the car- 

 rier of such varied and interesting considerations. 



The desire which I have frequently felt in my lectures of developing the 

 idea of the genus aldehyde, when speaking of the methyl-compounds, has 



