of Sciences of the Institute of France. 337 



fires, and shows still six peaks to which it may be wholly attri- 

 buted. It is the exact topography and mineralogy of one of 

 these six, that of Mont Peli^e, which M. de Jonnes has given us. 

 He believes that volcanic nature so general, that iie supposes it 

 serves even as a base to tliose of the Antilles, which present no- 

 tiiing but a calcareous exterior manifestly shelly, such as Bar- 

 L.idoes and the high land of Guadaloupe. Guadaloupe pro- 

 })erly so called is formed of four systems of eruption, one of 

 vhich,the S(mfnere,si\\\ maintains some degree of activity. M.de 

 Jonnes has also given a very accurate description of it in a ge- 

 neral statistical view of the island. 



Botany i 



One of the most important branches of botany, and which 

 more than any other connects it with the great body of physical 

 sciences, is vegetable geography, or the laws of the distribution 

 of plants according to the height of the pole, the elevation of 

 the soil, the temperature, and degree of humidity or dryness of 

 tiie climate. 



M. Humboldt, whose travels have contributed so much to the 

 progress of this as well as other branches of knowledge, has given 

 nearly a complete treatise on it under the title of Piolesnmenade 

 Distrilulinjie geographica Plantarum secundumCoeU Temperiem 

 et Altitudinem Mont'mm. In this work he presents some pro- 

 found researches on the distribution of heat, both relatively to 

 the positions of places and to tlie seasons of the year ; for not 

 only the lines under which the same mean annual degree of heat 

 prevails are far from being parallel to the equator, but places 

 which have upon the whole an equal mean heat have their sum- 

 mers and winters by no means alike. All these differences must, 

 it is conceived, have a strong influence on the propagation of 

 plants. The author afterwards proceeds to the differences which 

 result from elevation, and which are not regulated by the same 

 laws in all places : and he at last arrives at a consideration al- 

 together new, — that of the laws of the distribution of vegetable 

 forms. By comparing in eacli country the number of plants of 

 certain families well determined, with the total number of vege- 

 tables, he has found a striking regularity of numerical coinci- 

 dence. Certain sorts become more common in proportion as 

 we advance towards the pole ; others, on the contrary, increase 

 towards the equator ; while some attain their maximum in the 

 temperate zone, and are etjually diminished by too much heat and 

 loo much cold. And, which is very remarkable, this distribution 

 remains the same all over the globe, by following not the geo- 

 grapliic parallels, but what M. Humboldt calls isothcrmaL pa- 

 rallels, that is to say, lines of the same mean heat. So constant 

 Vol. ^19. No. 229. May lbl7. Y ^tie 



