1815.] Scientific Intelligence. 4G9 



prehension lias not yet been published. An autlior perhnps could 

 not he bet'er employed tlian in elucidating the principles of tliose 

 sciences rv'hich, iVoni iheir great and irrportar't applications, are so 

 int';ii;Ue!v connected v/nh the most profound and interesting depart- 

 ments of Itutnan V;no\viedge. 



I a:»j rvrT, however, a friend to tlie introduction of motion into 

 the "oncep'ion :>( H'..vional quruititios, as J conceive it to be foreign 

 to t'f.t ir.'juirv. 1 would rather consider the differential calculus as 

 an e\tei.' -l;;;! of the science of algebra. 



Your humble servant, 



Plymouth, }iii,yb, I8I5. George HarvEV. 



X. M'llky Juice of Plants. 



Dr. John has lately examined the milky juice of several European 

 plants. J conceive that a short account of the results which 1 e 

 c-b;;iined will be acceptable to the readers of the ylnnak of Plii- 

 lijjO[ilnj. 



1. IjeonloclonTaraociciim [DentrjUon). 

 The juice of this plant is liquid, and milk-white. It has a 

 sweetish and very bitter taste, with a certain des;rce of sharpness. 

 Its smell is biniilar to that of the fresh plant. When exposed to the 

 air, it speedily coagulates, and acquires a \iolet-brovvn colour. The 

 coagulated sa)) being boiled in water, communicates to that liquid a 

 brown colour and a bitter taste, and the property of reddening 

 litmus p-iper. The undissolved portion is white and elastic, and 

 similar to caoutchouc. It becomes brown by exposure to the air. 

 Alcohol acts but feebly on it, dissolving only a little resin. The 

 caoutchouc burns with a brilliant flame. The watery solution was 

 precipitated by oxalic acid, nitrate of silver, nitrate of mercury, and 

 nitrate of barytes. Hence the constituents of this plant are — 



Water. A trace of gum ? 



Caoutchouc. An acid. 



Bitter extractive. Muriate, phosphate, and sul- 

 A sweet substance ? phate of lime, and of an 



A trace of resin. alkali, 



2. Lacluca Sativa {Lettuce). 



This plant yields but little milky juice. According to John, its 

 properties are the same as those of the leontcdon taia\icuni, and its 

 constituents the same. He was not able to determine whether it 

 contained an uncombined acid. From the known soporific powers 

 of the juice of lettuce, there is reason to believe that it contains a ' 

 substance similar to that which exists in common oi)ium. It would 

 be worth while to examine wluther the juice of the leontodon 

 taraxicum contains the same principle. 



3. Ficiis Cnrica {tig Tret). 

 The twigs and footstalks of this tree yield a milky juice, whicU 



