composition, even at temperatures much, below that at which it melts. With regard to this resin, the author gives the following as the result of his numerous analyses : —
1. That the colourless resin of benzoin is represented approxi- mately by C40 Hoo Op.
2. That by heat and dilute carbonated alkalies it is decomposed into water, benzoic acid, a little volatile oil, and a resin C40H03 0,„ orC.oHo^O,.
3. That by boiling with quicklime, or concentrated carbonated alkalies, it gives two resins, one in large quantity = C40H04 O^; and another in small quantity = C_,q Hoq O^.
4. That by caustic potash the crude resin is resolved into two re- sins represented respectively by C40 Hoo O^, and C40 H30 O^, of which the former is precipitated, and the latter remains in solution, when a saturated aqueous solution of caustic potash is added to an alcoholic solution of the crude resin.
5. And that by oxide of lead two resins are separated, for which analysis gave respectively the formulae. C^qH^j^^j C4oHogOic.
The author concludes by stating that such metamorphoses are by no means confined to this resin, though the more accurate know- ledge of their nature, obtained by the imperfect study he has made of the resin of benzoin, has explained many anomalies he had pre- viously observed, ^^ith regard to the relations of the resins to the al- kalies and metallic oxides. He considers the group of which dragon's blood is the type, and which he represents by the expression C40 H04 + Og to be peculiarly susceptible of modification (or decomposition ?) by the action of bases ; and he specifies among other results, with regard to which it is his intention to address the Society in a future paper, that dragon's blood, of which the lump variety = C40 Hoi O^, and the drop variety (heated to 300° F.) = C40 Hoo gives by the action of quicklime and oxide of lead, among other products, two resins represented approximately by C40H00OJO and C40H00O10? — that guiacum =C4oHo3 0jo, 'vdth. oxide of lead, gives a resin = C40 Hoj Ojj, the resin of jalap = C40 H34 Ojg; by the action of the same oxide, a resin = C4oH34 0oo> and that of assafoetida = C40 Hog Ojq, a new resin = C40H03 O13. These metamorphoses lead to the second great branch of inquiry respecting the nature and constitution of the resins. Certain results being established, at least approximately, with regard to the irrational constitution of the resins, and certain general irrational formulae by which to express it, we are prepared for the study of their rational constitution. This part of the subject the author proposes to con- sider farther in subsequent communications.
8. Researches on the Tides. Twelfth Series. On the Laws of the Rise and Fall of the Sea's surface during each tide. By the Rev. W. Whewell, B.D., F.R.S., Fellow of Trinity College, Cam- bridge.
The materials of the present investigation are five months' tide observations made at Plymouth ; three months observations made
