Geology and Mineralogy. 159 



(and what proportion it is impossible to determine) is eliminated 

 from solution by the vital action of algae, and that algse are an 

 essential factor in producing many of the varied and beautiful 

 forms of the deposits in the Park. The fretted rims of the pools, 

 the coral-like and mushroom-like deposits, the "marble terraces" 

 and "petrified waterfalls" owe their physical characters, in part, 

 at least, to vegetable growth. The evidence seems conclusive, 

 and the author reviews the literature relating to hot springs in 

 various parts of the world, and deduces the inference that much 

 of the deposits about them, both calcareous or siliceous, are pro- 

 duced in the same way. The writer of this note has seen several 

 cases of both kinds of deposition, in each case accompanied with 

 algous growth, then considered an effect rather than a cause. The 

 most considerable was at the Steamboat Springs in Nevada, where, 

 upon the enormous mass of growing sinter there was an abun- 

 dant growth of minute alga3 of various and often brilliant colors, 

 flourishing luxuriantly in the warm gelatinous silica, the effect 

 made the more striking by a fierce snow storm which was raging. 

 Mr. Weed's conclusions are that plant-life is a very wide spread 

 and important agent in the production of travertine, tufas and 

 sinters. This is the more interesting, because within a few years 

 researches on the chemical functions of other low vegetable organ- 

 isms have shown that natural changes formerly supposed to be 

 due to purely chemical action are in reality dependent on vital or 

 physiological action in some way. Vitrification in soils, the de- 

 composition of sulphates in brackish waters are illustrations, and 

 Mr. Weed's observation extends our knowledge of the part that 

 vital action plays as a geological agent. w. h. b. 



3. Geological Survey of Illinois, A. H. Worthen, Director. 

 Vol. viii. Geology and Paleontology. 728 pp., 8vo, with an 

 Appendix of 152 additional pages. Illustrated by a portrait of 

 the distinguished head of the Survey (who died in May, 1888), 

 and a small geological map of the State; and also, under separate 

 covers, 78 lithographic plates of fossils. Edited by J. Lin- 

 dahl, Ph.D., State Geologist. — This volume completes the very 

 valuable series of reports of the Geological Survey of Illinois. 

 The series is second, among the State Geological reports of the 

 country, in the extent of its paleontological contributions, and 

 first, in the part of the paleontology relating to the Carboniferous 

 limestones. It contains, after an introduction by Mr. Lindahl, 

 chapters on the following subjects — (l) the Drift of Illinois, its 

 Coal, Natural Gas and Oil, and some fossil Invertebrates, by A. 

 H. Worthed, papers that were left unpublished by their author; 

 (2) new species of Crinoids and Blastoids from the Kinderhook 

 group of the Lower Carboniferous rocks at Le Grand, Towa, and 

 a new genus from the Niagara group of Western Tennessee, by 

 Charles Wachsmuth and Frank Springer; (3) American 

 Paleozoic Sponges, Sponges of the Devonian and Carboniferous 

 systems, and Paleozoic Bryozoa, by C. E. Ulrich ; (4) Descrip- 

 tions ot Lower Silurian Sponges, by E. O. Ulrich and Oliver 



