DIFFERENT VARIETIES OF SUGAR. 97 



colour (arising from the development of the carbon in a por- 

 tion of the sugar) which often ensues from the comparatively 

 high temperature necessary to effect the evaporation, under the 

 ordinary pressure of the atmosphere, as formerly conducted. 

 In connection with this subject, the nature of ebullition or boil- 

 ing was explained, and also the relations of the temperature at 

 which it takes place, to the atmospheric pressure to which the 

 boiling fluid is subjected, an illustrative experiment being per- 

 formed, by means of a modification of the Pulse-glass, in which 

 spirit of wine was made to boil violently, in a vacuum, merely 

 by the heat of the hand applied to the instrument. The ma- 

 nufacture of sugar-candy was also described. 



Some degree of general knowledge of the preparation and 

 nature of the vegetable principle called Sugar having thus 

 been imparted, the Classes were prepared to take an in- 

 terest in the history of its use, which was next briefly ex- 

 amined ; the notices of this substance occurring in the works 

 of Strabo, Varro, Dioscorides, and other ancient authors, 

 being mentioned, together with the allusions to it by old 

 travellers, as manufactured in the East, its introduction 

 into Western Europe during the Crusades, and the early cul- 

 tivation of the Sugar-cane in Sicily. The question as to its 

 being an indigenous production or not, of South America, 

 was also noticed, and the affirmative opinion adopted, and 

 supported by the citation of various authorities. 



The natural history of Sugar being now resumed, a view 

 was taken of the more important varieties which exist of this 

 substance, in addition to that yielded by the Sugar-cane. 

 The Sugars of Beet, Grapes, and Honey were briefly adverted- 

 to, the manufacture of Beet-Sugar in France, and that of 

 Grape-Sugar, by the chemist Proust, in Spain, being also 

 mentioned. The history of Maple-Sugar was given somewhat 

 more in detail, with an account of the tree (the Sugar Maple, 

 Acer saceharinum) in which it is contained in the form of sap, 

 and of the characters distinguishing it from Cane-Sugar. In 

 the consideration of this subject the following remarks were 

 introduced : " All the substances which result from organiza- 

 tion, or which are formed by the vital forces of animals or 

 vegetables, are peculiar in their nature in each organized being. 

 Thus, although muscular fibre, or flesh, is afforded by many 

 animals, and, in them all, consists of two animal substances, 

 culled jfibrine and gelatine ; while fibrine and gelatine are com- 

 posed of azote, carbon, hydrogen, and oxygen, in every animal, 

 yet the flesh of every class and indeed of every species of ani- 

 mals, is different. Thus, the flesh of the Mammalia is dis- 

 tinguished from that of Birds, and the flesh of Birds from that 



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