INDBX. 159 



Pitchstone, observations on the formation and varieties of, xii. 41. 

 Synopsis of its varieties, 51. Simple pitchstone, ib. Porphy- 

 ritic, 52, Concretionary spheroidal pitchstone, ib. Amygda- 

 loidal, containing imbedded nodules of another mineral, 53 



Place, observations on the changes of, in heavenly bodies, x, 9 



Placenta, observations on the nerves of, xix. 294 



Plagnb (M.), analysis of sea-water by, viii. 167 



Plague, supposed remedy for, vi. 379 



— of Athens, as described by Thucydides, vii. 125. Opinion 



of various ancient writers relative to its contagion, 126. His- 

 tory of that of Moscow in 1771, 134 



how introduced into Africa, viii. 183. Observations on 



the treatment of, 184 



remedy for, ix. 198 



Planariae, observations on, xx. 334 



Plana's (M.) researches relating to refraction, remarks on, xv. 



362 

 Planets, errors of the tables of, corrected, xi. 182 



small, places of, for the year 1822, xiii. 208 



Plantain-root, a febrifuge, x. 195 



Planting through trees, mode of, xviii. 409 

 Plants, experiments on the respiration of, iii. 199 

 ' how disseminated, iv. 1. Duration and death of annuals, 



biennials and perennials, 7. Observations on the longevity of 

 particular trees, 10; and on the effect of elevation above the 

 level of the sea upon the geography of plants in Fraijce, 176 



remedy for preventing injury to, from insects, vii. 170. 



Notices of various useful ones in the East Indies, 398 



geography of, defined, x. 239. History of, ib.., 240. 



On the number of known plants, and their distribution in va- 

 rious parts of the world, ib. Their geographical distribution, 

 241. Their social and solitary appearance, 254. AVhether, 

 and in what degree, the new and old worlds possess the same, 

 255. Comparative view of the temperature of both great con- 

 tinents, 25G. Influence of different altitudes upon the vegeta- 

 tion of, in the different zones of the earth, 202, Determina- 



