166 Dr, Colquhoun's Essay [Sept. 



semi-liquid consistence, large air-bubbles soon force their way 

 to its surface, where they break and dissipate in rapid succes- 

 sion. But where the sponge possesses the consistence of thin 

 doughy it confines this gaseous substance within it, until it 

 dilates equably and progresaively to nearly double its original 

 volume, when, no longer capable of containing the pent-up air, 

 it bursts and subsides. This process of rising and falling alter- 

 nately might be actively carried on and frequently repeated 

 during twenty-four hours, but experience has taught the baker 

 to guard against allowing full scope to the energy of the fer- 

 mentative principle. He generally interferes after the first, or 

 at furthest arterthe second or third dropping of the sponge, and 

 were he to omit this, the bread formed from his dough would 

 invariably prove sour to the taste and to the smell. 



He therefore, at this period, adds to the sponge the remaining 

 proportions of tlour and water, and salt, which may be necessary 

 to form the dough of the required consistence and size ; and 

 next incorporates all these materials with the sponge by a long 

 and laborious course of kneading. When this process has been 

 continued until the fermenting and the newly-added flour 

 have been intimately blended together, and until the glutinous 

 particles of the flour are wrought to such a union and consist- 

 ence, that the dough, now tough and elastic, will receive the 

 smart pressure of the hand without adhering to it when with- 

 drawn, the kneading is for a while suspended. The dough is 

 abandoned to itself for a few hours, during which time it conti- 

 nues in a state of active fermentation now diftused through its 

 whole extent. After the lapse of this time, it is subjected to a 

 second, but much less laborious kneading, the object of which is 

 to distribute the gas engendered within it as equably as possible 

 ^"throughout its entire constitution ; so that no part of the dough 

 ^^ay form a sad or ill-raised bread from the deficiency of this 

 t^arbonic acid gas, on the one hand, or a too vesicular or spongy 

 f>'bread from its excess, on the other. After the second kneading, 

 ; the dough is weighed out into the portions requisite to form the 

 ' kinds of bread desired : these portions of dough are shaped into 

 loaves, and once more set aside for an hour or two in a warm 

 situation. The continuance of fermentation soon generates a 

 sufficient quantity of fresh carbonic acid gas within them to 

 expand each mass to about double its former volume. They 

 are now considered fit for the fire, and are finally baked into 

 loaves, which, when they quit the oven, have attained a size 

 nearly twice as bulky as that at which they entered it. It 

 should be remarked that the generation of the due quantity of 

 elastic fluid within the dough has been found absolutely neces- 

 sary to be complete 7»e/bre placing it in the oven; because, as 

 soon as the dough is there introduced, the process of fermenta- 

 tion is checked, and it is only the previously-contained air, 



