168 A Tribute to the Memory of [Sept. 



The essay on Ferments and Fermentation is valuable, not for 

 the theoretical speculations which it contains, for these have 

 been superseded by subsequent discoveries ; but for a few facts 

 of considerable importance. It was at that time believed that 

 the infusion of malt, called icort, could not be made to ferment, 

 without the addition of yeast or barm ; but Mr. Henry disco- 

 vered that wort may be brought into a state of fermentation by 

 being impregnated with carbonic acid gas. By a fermentation 

 thus excited, he obtained not only good beer, but yeast fit for 

 the making of bread ; and, from separate portions of the fer- 

 mented liquor, he procured also ardent spirit and vinegar, thus 

 proving that the fermentative process had been fully completed. 

 He found, moreover, that flour and water, boiled to the consist- 

 ency of a thin jellv, and impregnated with carbonic ac;d in a 

 Nooth's machine, passed into fermentation, and by the third day 

 had assumed the appearance of yeast, for which it served as a 

 tolerable substitute in the making of bread. 



The other memoir, which is distinguished by its value and 

 importance, is entitled, Considerations relative to the Nature of 

 Wool, Silk, and Cotton, as Objects of the Art of Dyeing ; on 

 the various Preparations aid Mordants requisite for these 

 different Substances ; and on the Nature and Properties of 

 Colouring Matter. 



After having given a general view of the history of the art of 

 dveing, Mr. Henry, in this elaborate essay, examines the theo- 

 ries that had been framed to account for the various facility and 

 permanency with which different substances attract colouring 

 matter. He demonstrates the futility of those hypotheses that 

 explained the facts by supposed peculiarities of mechanical 

 structure in the materials to be dyed ; aud suggests the probabi- 

 lity that the unequal powers of absorbing and fixing colouring 

 matter, manifested by wool, silk, linen, and cotton, depend on 

 the different attractions, inherent in those substances as chemical 

 compounds, for the various colouring ingredients. All the pre- 

 paratory operations, though differing for each material, have, he 

 apprehends, one common object; viz. the removal of some 

 extraneous matter which, being already united with the sub- 



(2.) Observations on the Inficence of Fixed Air on Vegetation, anil on the 

 probable Cause of the Difference in the Results of various Experiments made for 

 that Purpose. 



In vol. ill. (1.) Observations on the Bills of Mortality for the Towns of Man- 

 chester and Salford. 



(2.) Case of a Person becoming short-sighted in advanced Age. 



(3.1 Considerations relative to the Nature of Wool, Silk, and Cotton, as Objects 

 of the Art of Dyeing; on the various Preparations and Mordants requisite for 

 these different Substances; and on the Natureand Properties of Colouring Matter, 

 together with some Observations on the Theory of Dyeing in general, and particu- 

 larly the Turkey-Red. 



New Series, vol. ii. Remarks on Mr. Nicholson's Account of the Effects pro- 

 duced at Swintonb\ a Stroke of Lightning. 



And a paper, printed in this volume, entitled Memoirs of the late Charles 

 Wh'le, Esq. E.R.S. chiefly with a Reference to his profession! Life and Writings. 



