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THE POPULAR SCIENCE MONTHLY. 



is this habit fixed, however, that, even where 

 a tree stands alone, its trunks and branches 

 are almost invariably covered with these 

 plants. Their abundance and variety may 

 be judged from the fact that upon a single 

 jicara tree, not more than twenty feet high, 

 which stood in a clearing near Castillo, the 

 author counted forty species of epiphytes. 

 The vines and underbrush are less abundant 

 on the higher grounds, and moving about is 

 consequently easier. But, whether the place 

 is high or low, the same deep, dark, reeking 

 forest spreads over all. Two facts strike the 

 observer as peculiar, at least during the sea- 

 son which the party spent at Castillo the 

 comparative scarcity of brilliant flowers, and 

 the failure of the plants of one species to 

 mass together. The comparatively small 

 number of conspicuous flowers is a disap- 

 pointment to him who expects to find a mass 

 of brilliant bloom in these tropical forests ; 

 not so much because these flowers are really 

 wanting as because the flowering period of 

 most of the species is rather long, and for 

 the further, perhaps more important, reason 

 that the flowers which do appear seem insig- 

 nificant when compared with the sea of green 

 that covers everything. No less striking is 

 the fact that, as a rule, specimens of any one 

 species do not mass together to the exclusion 

 of other species, excepting sometimes along 

 the watercourses. Different kinds of trees 

 are mingled together in endless confusion, 

 and no " groves " of any one species, such 

 as we are familiar with in the North, occur, 

 nor can any species, as a rule, ever be said 

 to be prominent. The same is true of smaller 

 plants ; and the collector is not only bewil- 

 dered by the variety of plants that come in 

 his way, even in a restricted locality, but is 

 also provoked by the scarcity of specimens 

 of most of the species. Along the river 

 banks, however, palms, grasses, etc., often 

 take possession of large tracts. 



Origin of Clays. Clay, says Mr. Robert 

 T. Hill, in his report on that material in the 

 " Mineral Resources of the United States," 

 is the immediate or ultimate product of the 

 decomposition of feldspar. Feldspar is a con- 

 stituent mineral of all the igneous rocks of 

 the earth, and is especially abundant in the 

 older granites and gneisses. By its decom- 

 position, which occurs principally under the 



action of water, the soda, lime, potash, and 

 other alkaline constituents of the feldspar 

 are removed in solution, leaving the alumi- 

 num silicate and quartz as a residuum, com- 

 mercially known as rock kaolin a non-plastic 

 material which, when free from iron, is also 

 known as porcelain clay. Water, in Nature 

 as in pottery, is the chief agent in clay work- 

 ing, and, besides its original action in decom- 

 posing the feldspar, it transports and grinds 

 the original kaolin, and deposits it, in vari- 

 ous degrees of purity or mixture, in second- 

 ary localities as a sediment. Clay material 

 thus produced is known as sedimentary or 

 transported clay, and, with the exception of 

 some of the kaolins which have not been far 

 removed from their place of origin, is more 

 or less plastic. The washing and grinding 

 of clays by clay-workers is a repetition of 

 fundamental geologic processes of erosion, 

 corrosion, and deposition constantly going on 

 in Nature ; and the geologist can see in the 

 flumes and settling tanks of the potter a 

 laboratory demonstration of the principal 

 agencies which he studies. The clay mate- 

 rial resulting from the decay of feldspar may 

 be broadly classified under the two general 

 heads of residual and sedimentary. The re- 

 sidual material is that which is found in the 

 original place of occurrence of the decom- 

 posing feldspar, and may possess many phys- 

 ical aspects, sometimes occurring as a firm 

 or crumbling rock, resembling decomposed 

 granite, or again as a fine, white, non-plastic 

 clay or kaolin. It is usually accompanied by 

 quartz, a material not essentially injurious, 

 which can be removed, if that is desired, by 

 washing. The sedimentary clays are those 

 which have been removed from their place 

 of origin and redeposited in water. They 

 embrace all degrees of mixture and purity, 

 and may be either kaolinitic or plastic. 



Value of a Geological Survey. On the 



18th of April, 1894, the geological survey of 

 Alabama attained its majority twenty-one 

 years under the present management, with 

 Eugene A. Smith as State Geologist. By 

 way of memorial of the occasion maps are 

 in course of preparation showing the condi- 

 tion of our knowledge of the geology of the 

 State at the beginning and at the end of the 

 period, 1873 to 1894 ; and besides these, 

 tables showing the relative amounts of raw 



