2 THE POPULAR SCIENCE MONTHLY. 



boiler; this is almost as true as to mental as it is to physical 

 power. 



There are innumerable treatises upon the feeding of animals ; 

 upon the generation of steam ; upon the construction and ventila- 

 tion of buildings ; upon the arts which relate to clothing the hu- 

 man body, and upon keeping the dwelling and workshop warm ; 

 and, lastly, yet more numerous treatises or cookery-books upon 

 the art of mixing and preparing the food which is to be cooked ; 

 there are also many treatises, chemical and physiological, upon 

 the subject of nutrition, and there are one or two treatises on the 

 science of cooking, notably Dr. Mattieu Williams's " Chemistry of 

 Cookery " ; yet, so far as the writer has been able to ascertain the 

 facts, there is no receipt-book or cookery-book in common use 

 which deals with the actual art of cooking by directing the right 

 application of heat for a suitable time and at a suitable degree, to 

 the specific food which is to be converted into a nutritious form 

 by the conversion of its elements into new forms or conditions by 

 the action of heat upon it. 



It is possible that greater attention has been given to this mat- 

 ter in England than in this country. After trying in vain to find 

 an oven thermometer in the United States, I lately imported one 

 from England, made by Joseph Davis & Co., Fitzroy Works, Lon- 

 don, S. E., and purchased at an agricultural show at retail for 

 seven shillings sixpence, gauged at 200 to 600 Fahrenheit. On 

 this thermometer are marked the respective degrees to which vari- 

 ous kinds of food should be subjected, as follows : 



Pork 320 Fahr. 



Veal 320 " 



Beef 310 " 



Mutton 300 " 



Puff pastry 340 Fahr. 



Bread 340 " 



Pastry 320 " 



Meat-pie 290 " 



These figures agree substantially with my own experiments as 

 to the maximum of heat, but I do not concur with the inference 

 that less than 200 Fahr. may not be permitted, if time be given 

 for the lower degree of heat to do its work. On the contrary, any 

 kinds of very tough meat may be reduced to a very tender condi- 

 tion by the long application of heat at 180 to 200, without loss of 

 flavor or nutritious property, provided the food be put into sub- 

 stantially air-tight vessels. The testimony of Dr. Mattieu Will- 

 iams is conclusive on this point, as well as the special knowledge 

 of the few good cooks of the method of simmering as distin- 

 guished from boiling. Meats and grains may be most nutritiously 

 cooked at less than a boiling heat, and eggs should always be ; 

 while most kinds of roots, tubers, and vegetables require a higher 

 degree. 



I venture now to give some of the general conclusions which I 

 have reached by the application of somewhat crude methods and 



