1856.] Mr, Huxley^ on Natural History, 187 



more northern ones from traversing a wider tract of sea, confers a 

 temperate, moist, and oceanic climate upon the Pacific slope ; but 

 deprived largely of its moisture by ascending the high mountain 

 barrier of the Pacific chain, which robs it of nearly the whole of 

 its wetness, it exerts in the more southern latitudes just the opposite 

 effect upon the plains and table lands to the leeward or eastward 

 of that barrier. The high evaporative power of the winds thus 

 parched accounts for the excessive aridity of the Colorado and 

 Utah deserts, and the whole desert belt of the interior, which in 

 the lower latitudes stretches to Texas. It likewise explains the 

 prevalence of numerous salt lakes, destitute of outlets, and the 

 occurrence of the wide tracts covered with salt, or with a saline 

 soil, within this area. 



Gold. — To the same general cause, the Pacific wind, we are to 

 attribute the abundant gold alluvia of the western slope and base 

 of the Sierra Nevada. The copious precipitation of rain, amounting 

 to nearly the whole humidity of the Pacific wind, against the gold- 

 containing western flank of the Californian chain, greater probably 

 in the pleistocene than in the modern epochs, has produced an 

 enormous erosion of the gold-bearing and cleavage fissured rocks; 

 and has strewn and sorted their fragments and particles in the 

 ravines of the mountain, and in the plains at its base. The speaker 

 concluded with an announcement of the general fact that, whereas 

 the salt-fields of the earth are found upon the continental or interior 

 dry sides of its oceanic chains, its gold-fields are restricted to their 

 wet or oceanic slopes. 



[H. D. R.] 



WEEKLY EVENING MEETING, 



Friday, February 15. 



Sir IIeney Holland, Bart. M.D. F.R.S. Vice-President, 

 in the Chair, 



Thomas Henby Huxley, Esq. F.R.S. 



FULLEBIAN PROFESSOR OF PHYSIOLOGY, R.I. 



On Natural History^ as Knowledge, Discipline, and Power, 



The value of any pursuit depends upon the extent to which it fulfils 

 one or all of three conditions. Either it enlarges our experience ; 

 or it increases our strength ; or it diminishes the obstacles in the 

 way of our acquiring experience and strength. Whatever neither 

 teaches, nor strengthens, nor helps us, is either useless or mischievous. 



