196 ANNUAL OF SCIENTIFIC DISCOVERT. 



precious and bring great prices. He determined by actual experiment 

 which of the two methods was the best. He burned carefully a pound 

 of good Mocha, and separated it into two equal portions. The one 

 was passed through the mill, the other beaten, after the Turkish fashion, 

 in a mortar. He made coffee of each. Taking equal weights of each, 

 and pouring on an equal weight of boiling water, he treated them both 

 precisely alike. He tasted the coffee himself, and caused other com- 

 petent judges to do so. The unanimous opinion was, that coffee beaten 

 in a mortar was far better than that ground in a mill. And after men- 

 tioning that any may repeat the experiment, he tells a strange anec- 

 $ote of the influence of one or the other kind of manipulation, namely: 

 " Monsieur," said Napoleon, one day, to Laplace, " how comes it that 

 a glass of water into which I put a lump of loaf sugar tastes more pleas- 

 antly than if I had put in the same quantity of crushed sugar ?" " Sir," 

 said the philosophical senator, " there are three substances, the con- 

 stituents of which are identical sugar, gum, and starch ; they differ 

 only in certain conditions, the secret of which nature has preserved. 

 I think it possible that in the effect produced by the pestle, some sac- 

 charine particles become either gum or amidon, and cause the differ- 

 ence." Boston Transcript. 



THE DISSOCIATION OF WATER. 



This term will seem strange to English ears, but perhaps not more 

 so than its equivalent, " la dissociation de I'eau " to the French, and at 

 any rate it seems most advisable to preserve the name given by M. H. 

 St. Claire Deville to the very interesting phenomena described by him 

 to the French Academy, in a paper of which we proceed to give an 

 account. 



M. Deville commences by stating that if a tolerably rapid cur- 

 rent of hydrogen is made to traverse a porous earthen tube and the gas 

 which escapes is collected, it is found to be, not hydrogen, but in round 

 numbers, oxygen twenty-one, and nitrogen seventy-nine. "Thus the 

 hydrogen is dispersed through the atmosphere, and air is absorbed by 

 the porous tube in virtue of endosmose, and in spite of the pressure of 

 some centimetres of water, or mercury, into which the abducting tube 

 is plunged, and which is maintained in the interior of the apparatus." 

 If the porous tube is introduced into an impermeable porcelain tube, 

 shorter than itself, and closed at each end with a cork, through which 

 the porous tube is inserted, a space is enclosed into which any kind of 

 gas can be admitted. For this purpose, the corks are pierced so as to 

 admit an exit and entrance tube of glass. The porous tube is similarly 

 provided, and if a current of carbonic acid gas is made to traverse the 

 space between the porous tube and the porcelain tube, while hydrogen 

 is driven through the former, the hydrogen changes its place, and may 

 be inflamed at the exit where the carbonic acid might have been ex- 

 pected, while the porous tube allows nearly pure carbonic acid to es- 

 cape. These facts, observes M. Deville, are in accordance with the 

 observations of Professor Graham and M. Jamin. 



If the preceding apparatus is placed in a furnace supplied with dense 

 fuel, affording a heat of 1100 to 1300 (C.), it will suffice to demon- 

 strate the spontaneous decomposition of water, a phenomenon which 

 M. Deville terms dissociation. To accomplish this, vapor of water is 



