130 M. Dumas on the Constitution of Milk and Blood, 



ciate at a glance the importance of the questions which were 

 addressed to them, the insufficiency of the means at their 

 command during those troublous times, and the merits of the 

 practical solutions which they presented to the country, as the 

 fruit of their previous studies, or of their improvised experi- 

 ments. 



Saltpetre, gunpowder, steel, weapons, gun-metal, potash, 

 soda, soaps, paper, assignats, and many other objects impli- 

 cated in the defence of the country, the working of its manu- 

 factures and the necessaries of life, gave occasion to investi- 

 gations and discoveries of which the factories have not yet 

 forgotten the tradition. 



The siege of Paris by the Prussian army could not, it was 

 said, be sufficiently prolonged to raise any questions of the 

 same kind j but nevertheless it has been necessary, as in the 

 time of our fathers, to seek for nitrated earths, to produce 

 gunpowder, to manufacture and work up steel, to obtain 

 bronze and cast cannon ; we also have been in want of paper, 

 and of a great number of useful objects. 



Considerable, although rapid, investigations have been 

 accomplished ; and it will be useful as well as just not to allow 

 their memory to be lost. I have busied myself in collecting 

 the materials for this publication, which I shall carry out as 

 soon as circumstances will permit. 



Among the privations which our forefathers did not know 

 in their most cruel intensity, those which caused the most 

 decided sufferings to the existing population, relate to the 

 want of combustibles, which was rendered intolerable and most 

 destructive by an exceptionally rigorous winter — to the scar- 

 city of milk and eggs, the certain cause of the premature 

 decease of a great number of young children— and, finally, to 

 the exhaustion of the supplies of corn, flour, and meat, which, 

 rendering the capitulation of Paris inevitable, marked the 

 precise day for it. 



Three questions, which have occupied the mind of every 

 man curious to foresee the future of science, were thus inces- 

 santly presented to the meditation of the scientific men shut 

 up in Paris, not as far-away dreams in which the imagination 

 delights and disports itself, but as the despairing prayers of a 

 people in utter extremity : — 



1. To obtain available heat, without combustibles; 



2. To reconstruct food with mineral materials, without the 



cooperation of life ; 



3. To reproduce, at least, the essential food of man with 



non-alimentary organic materials. 

 Man, in warming himself by means of combustibles furnished 



