77 6 THE POPULAR SCIENCE MONTHLY. 



economy of fuel is practiced in conducting it, and therefore less disso- 

 ciation would be effected than in the domestic retail process. 



Some of the early manufacturers of "bosch" purified their fat by 

 the process recommended and practiced by the French Academicians 

 MM. Dubrunfaut and Fua (see " Comptes Rendus," vol. lxxi) during the 

 siege of Paris, when they and others read papers on the manufacture 

 of "siege-butter" without the aid of the dairy. This consisted in 

 frying the refuse fat from slaughter-houses until the membranous 

 matter and other impurities were carbonized, and thus could be strained 

 away. I wrote about it in 1871, and consequently received some sam- 

 ples of artificial butter thus made in the midlands. It was pure fat, 

 perfectly wholesome, but, although colored to imitate butter, had the 

 granular character of dripping. Since that time great progress has 

 been made in this branch of industry. I have lately tasted samples of 

 pure " bosch " or " oleomargarine " undistinguishable from churned 

 cream or good butter, though offered for sale at S^d. per pound in 

 wholesale packages. In the preparation of this I understand high tem- 

 peratures are carefully avoided, and by this means the smoothness of 

 pure butter is obtained. I mention this now merely in confirmation 

 of my theory of the rationale of fat-cookery, but shall return to this 

 subject of " bosch " or " butterine " again, as it has considerable intrin- 

 sic interest in reference to our food-supplies, and should be better un- 

 derstood than it is. 



XXVII. 



The cookery of milk is very simple, but by no means unimportant. 

 That there is an appreciable difference between raw and boiled milk 

 may be proved by taking equal quantities of each (the boiled sample 

 having been allowed to cool down), adding them to equal quantities 

 of the same infusion of coffee, then critically tasting the mixtures. 

 The difference is sufficient to have long since established the practice 

 among all skillful cooks of scrupulously using boiled milk for making 

 cafe au lait. I have tried a similar experiment on tea, and find that 

 in this case the cold milk is preferable. Why this should be, why 

 boiled milk should be better for coffee and raw milk for tea, I can not 

 tell. If any of my readers have not done so already, let them try 

 similar experiments with condensed milk, and I have no doubt that 

 the verdict of the majority will be that it is passable with coffee, but 

 very objectionable in tea. This is milk that has been very much 

 cooked. 



The chief definable alteration effected by the boiling of milk is 

 the coagulation of the small quantity of albumen which it contains. 

 This rises as it becomes solidified, and forms a skin-like scum on the 

 surface, which may be lifted with a spoon and eaten, as it is perfectly 

 wholesome and very nutritious. 



If all the milk that is poured into London every morning were to 



