14 Professor Johnston on the Sugar of the Eucalyptus. 



But V will not serve for the equations of the disturbing body. 

 If we wish to find integral equations of the first order, we 

 should have a perturbating function which will serve for two 

 at least of the three sets of equations (A.). 



My paper on M. Jacobi's Theory of Elliptic Functions, 

 printed in the Number of this Journal for the present month, 

 is not very intelligible. I wish, therefore, to subjoin a few 

 words in the hope of making it plainer. The expressions sin 

 amtico, cos am n oo, mean sine of amplitude of n w, cosine of 

 amplitude of n ca. So also s au, c au mean sine and cosine of 

 the amplitude of u. They should have been printed thus : — 

 sin am n ca, cos am n co, s au, c au. These faults run through 

 the paper. Moreover the a m and a for amplitude should not 

 have been in italics, as italics appear to denote quantity only. 

 Denby, near Huddersfield, April 11, 1843. 



V. On the Sugar of the Eucalyptus. 

 By James F. W. Johnston, Esq., M.A., F.R.S.* 



TN Van Diemen's Land a species of sugar or manna falls 

 in drops or rounded opaque tears from several species of 

 Eucalyptus. This is collected in considerable quantity, but 

 it is doubtful still I believe whether it is a natural exudation 

 of the trees from which it falls, or, like the different kinds of 

 honey-dew in our own country, is the consequence of punc- 

 tures made by insects. 



I am indebted for a portion of this manna to Sir W. 

 Jackson Hooker, to whom also I owe the above information 

 regarding its origin. It is soft, slightly yellowish, opaque, is 

 inferior in sweetness to cane-sugar or to ordinary manna, and 

 is in small, rounded, slightly cohering masses. iEther extracts 

 from it only a minute portion of wax, alcohol leaves behind 

 only a small quantity of gum, while water dissolves it without 

 sensible residue. 



The aqueous solution crystallizes on evaporation in minute 

 radiating prisms and prismatic needles which form rounded 

 masses having a crystalline structure. It is obtained however 

 from water in distinct crystals with much greater difficulty 

 than from its solution in ordinary alcohol. In boiling alcohol 

 it dissolves in considerable quantity, and is in a great measure 

 precipitated in beautiful white but minute prismatic crystals 

 as the solution cools. It not unfrequently deposits itself also 

 in the form of a white hard and solid crust on the bottom and 

 sides of the bottle into which the hot solution is filtered. 



This sugar as it crystallizes from the alcoholic solution has 



* Communicated by the Chemical Society; having been read De- 

 cember 20, 1842. 



