Chap. 5.3 Manna, 47 



the loaves are carried to an oven to dry. At the end of 

 eight or ten days thefe loaves are broken, and the 

 powdered fugar is conveyed to Europe. 



Certain juiqes which flow out of plants are of a fac- 

 charine nature ; fuch is manna, which is produced by 

 the pine, the fir, the oak, the maple, the juniper, the 

 fig, the willow, &r. ; but the afli ; the larch, and the 

 alhagi afford it in the largeft quantities. Robel, Ron- 

 delet, and others, have obferved at Montpelier, upon 

 the olive trees, a kind of manna, to which they hare 

 given the name of oeliomeli. Tcurnefort collected it 

 from the fame trees at Aix and Toulon. The am, 

 which is very abundant in Calabria and Sicily, affords 

 the manna of commerce : it flows fpontaneoufly from 

 thefe trees, but is much more abundantly collected by 

 making incifions in the bark. That which is procured by 

 introducing chips of wood or fmall flicks into artificial 

 apertures, forms a kind of ftalactites, perforated within, 

 and called manna in the tear. Manna in flakes flows 

 from the bark, and contains fome impurities. Manna 

 affords, by treatment with the nitrous acid, the fame 

 acid as is obtained from fugar. 



III. FAT OILS are not emitted from the furface of 

 vegetables, but are obtained by prefiure from their 

 emulfive feeds or kernels. They feel fmooth to the 

 touch, are generally, when recent, without fmell or 

 tafle, and are infoluble in water. They are not vola- 

 tilized but by a heat confiderably fuperior to that of 

 boiling water, and do not take fire till fufficiently heated 

 to be volatilized. When they are burned on the wick 

 of a lamp, fmall portions are fuccefllvely brought to 

 its extremity, and being there volatilized, undergo in- 

 flammation. Moft fat oils are fluid, and require a con- 

 fiderable degree of cold to congeal them -, others be- 

 come 



