DISTRIBUTION OF NORTH AMERICAN FORESTS. 517 



The difference of time is so great that the smaller relative surface 

 is insufficient to compensate for the evaporation that must occur if the 

 grilling principle, or the pure and simple action of radiant heat, were 

 only made available, as in the above ideal roasting of the small joint. 



What, then, is added to this ? How is the desiccating difficulty 

 overcome in the large-scale roasting ? Simply by basting. 



All night long and all the next morning men were continuously at 

 work pouring melted fat over the surface of the slowly-rotating car- 

 cass of the Warwick ox, skillfully directing a ladleful to any part that 

 indicated undue dryness. 



By this device the meat is more or less completely enveloped in 

 a varnish of hot melted fat, which assisted in the communication of 

 heat while it checked the evaporation of the juices. In such roasting 

 the heat is partially communicated by convection through the medi- 

 um of a fat-bath, as in stewing it is all supplied by a water-bath. 



I purpose making an experiment, whereby this principle will be 

 fully carried out. I shall melt a sufficient quantity of mutton-fat to 

 form a bath, in which a small joint of mutton may be immersed, or of 

 beef -fat for beef ; and then keep the melted fat at about the cooking 

 temperature, or a little above it say the boiling-point of water, which 

 will be indicated by the spluttering due to the evaporation of the 

 water in the meat. The result of this experiment will be duly re- 

 ported to the readers of "Knowledge" when I reach the general sub- 

 ject of frying. In my next I must continue this subject of roasting, 

 which is by no means exhausted yet. Count Rumford devotes sev- 

 enty pages to it, and I quote his words for my own use. He says : 

 " I shall, no doubt, be criticised by many for dwelling so long on a 

 subject which to them will appear low, vulgar, and trifling ; but I 

 must not be deterred by fastidious criticisms from doing all I can do 

 to succeed in what I have undertaken. Were I to treat my subject 

 superficially, my writing would be of no use to anybody, and my labor 

 would be lost ; but by investigating it thoroughly I may, perhaps, 

 engage others to pay that attention to it which, from its importance, 

 it deserves." * Knowledge. 







THE GEOLOGICAL DISTRIBUTION" OF NORTH AMERI- 

 CAN FORESTS. 



By THOMAS J. HOWELL. 



THE causes which have determined the present distribution of the 

 flora of the world have occupied the minds of some of the ablest 

 students of natural history, but no satisfactory solution of the problem 

 has yet appeared. If we accept the theory of Raumer, that plants are 

 * "Essays Political, Economical, aDd Philosophical," vol. iii, p. 129. 



