384- Royal Society. 



and Rose. The Bdellium of commerce contains much gum, and a 

 resin C 40 H 31 O,,. 



The resin of Benzoin presented peculiar difficulties when sub- 

 mitted to investigation, from the ease with which it undergoes de- 

 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 C 40 H 22 O 9 . 



2. That by heat and dilute carbonated alkalies it is decomposed 

 into water, benzoic acid, a little volatile oil, and a resin C 40 H 03 O c , 

 orC 40 H 24 0,,. 



3. That by boiling with quicklime, or concentrated carbonated 

 alkalies, it gives two resins, one in large quantity = C 40 H 24 O s ; and 

 another in small quantity = C 40 H 30 O 7 . 



4. That by caustic potash the crude resin is resolved into two re- 

 sins represented respectively by C 40 H 22 O s , and C 40 H 30 O 7 , 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 40 H 22 O,,, 'and C 40 Ho 6 O 10 . 



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, with 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 

 C 40 H 24 + x O g 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 = C 40 H 21 O 8 , and the drop variety (heated to 300 F.) 

 = C 40 H 20 O 8 , gives by the action of quicklime and oxide of lead, 

 among other products, two resins represented approximately by 

 C 4 o H 20 O, and C 40 H 20 O 12 ? that guiacum = C 40 H 23 O, , with 

 oxide of lead, gives a resin = C 40 H 21 O n , the resin of jalap 

 = C 40 H 34 O, 8 ; by the action of the same oxide, a resin = C 40 H 34 O 20 , 

 and that of assafcetida = C 40 H Q6 O, , a new resin = C 40 H 23 O 13 . 

 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 



