[viii] 



COSMOS. 



and mountain chains. The degree of heat at the surface of the sea in diffe- 

 rent latitudes and in the lower strata. Tendency of the sea to maintain 

 the temperature of the surface in the strata nearest to the atmosphere, 

 in consequence of the mobility of its particles, and the alteration in its 

 density. Maximum of the density of salt water. Position of the zones 

 of the hottest water, and of those having the greatest saline contents. 

 Thermic influence of the lower polar current and the counter-currents 

 in the straits of the sea pp. 306-309 and notes. General level of the 

 sea, and permanent local disturbances of equilibrium; the periodic 

 disturbances manifested as tides. Oceanic currents ; the equatorial or 

 rotation current, the Atlantic warm Gulf-stream, and the further im- 

 pulse which it receives; the cld Peruvian stream in the eastern portion 

 of the Pacific Ocean of the southern zone. Temperature of shoals. The 

 universal diffusion of life in the ocean. Influence of the small sub- 

 marine sylvan region at the bottom of beds of rooted algse, or on 

 far-extending floating layers of fucus pp. 309-316 and notes. 



h. The gaseous envelope of our planet, the atmosphere. Chemical 

 composition of the atmosphere, its transparency, its polarisation, pres- 

 sure, temperature, humidity, and electric tension. Relation of oxygen 

 to nitrogen; amount of carbonic acid; carburetted hydrogen; ammo- 

 niacal vapours. Miasmata. Regular (horary) changes in the pres- 

 sure of the atmosphere. Mean barometrical height at the level of 

 the sea in different zones of the earth. Isobarometrical curves. Baro- 

 metrical windroses. Law of rotation of the winds, and its importance 

 with reference to the knowledge of many meteorological processes. 

 Land and sea winds, trade winds and monsoons pp. 316-322. Climatic 

 distribution of heat in the atmosphere, as the effect of the relative posi- 

 tion of transparent and opaque masses, (fluid and solid superficial area,) 

 and of the hypsometrical configuration of continents. Curvature of the 

 isothermal lines in a horizontal and vertical direction, on the earth's sur- 

 face and in the superimposed strata of air. Convexity and concavity of 

 the isothermal lines. Mean heat of the year, seasons, months, and days. 

 Enumeration of the causes which produce disturbances in the form of 

 the isothermal lines, i. e. their deviation from the position of the geogra- 

 phical parallels. Isochirnenal and isotheral lines are the lines of equal 

 winter and summer heat. Causes which raise or lower the temperature. 

 Radiation of the earth's surface according to its inclination, colour, 

 density, dryness, and chemical composition. The form of the cloud 

 which announces what is passing in the upper strata of the atmosphere 

 is the image of the strongly radiating ground projected on a hot sum- 

 mer sky. Contrast between an insular or littoral climate, such as is 

 experienced by all deeply-articulated continents, and the climate of the 

 interior of large tracts of land. East and west coasts. Difference be- 

 tween the southern and northern hemispheres. Thermal scales of culti- 

 vated plants, going down from the vanilla, cacoa, and musacete, to citrons, 

 and olives, and to vines yielding potable wines. The influence which 

 these scales exercise on the geographical distribution of cultivated plants. 

 The favourable ripening and the immaturity of fruits are essentially influ- 

 enced by the difference in the action of direct or scattered light in a 



