256 ANNUAL OF SCIENTIFIC DISCOVERT. 



afterward appeared "was more likely to be herbaceous than 

 arboreal," because the seeds must have been l)r()u;^ht from dis- 

 tant regions. Mr. Lesquereux considers that the prairies were 

 formed by a process of natural reclamation from the borders of 

 lakes, mouths, and banks of large rivers, and coasts of seas 

 (fresh water and salt), and cites, in illustration, the cases of the 

 Mississippi, Lake ^Michigan, etc. lie thinks that the nature of 

 the soil formed under tiiese circumstances would be such as to 

 favor only the growth of sedges and grasses ; and he endeavors 

 to show that his explanation will account for the existence of all 

 known prairies and large ilat tracts of land, including "the nat- 

 ural meadows of llidland," etc. Prof. Dana advances an explan- 

 ation of a totally dillVrent nature, namely, that the absence of 

 forests and presence of prairies are caused by the dryness of the 

 climate, while conversely the presence of forests is caused by its 

 moisture. Prof. Dana's facts are indisputable and generally re- 

 ceived, for every one acknowledges the intimate relation of the 

 moisture of the climate to the existence of forests; the only ques- 

 tion is, which is the cause and which the eftect. Experience has 

 shown that the moisture of a climate may be increased by plant- 

 ing forests, and diminished by clearing them. — Quarterly Journal 

 of Science, April, 18G6. 



ARTESIAN WELLS OF CHICAGO, ILLINOIS. 



These wells, now discharging 1,250,000 gallons per day of the 

 purest water, are located near the city limits, about three miles from 

 the City Hall ; they are 700 feet deep, and discharge an immense 

 amount of clear cold water. In several respects these wells are 

 anomalies ; first, the water which rises to the surface stands at 

 57° Fahr., which is below the mean temperature of the locality, 

 while in all other deep wells the temperature increases in pro- 

 portion to the descent, so that no water is found at a greater 

 depth at much less than 75° ; and in the great wells at Charles- 

 ton and in the basin at Paris the range is up to 85° and 90°. Then 

 this water is free from the unpleasant and disagreeable mineral 

 taints so common to Artesian wells. It is certified, under chemical 

 analysis, to be the best ax ticle o f^drinking water in the world ; and 

 from the force and power witTi which it comes to the surface, it 

 has a head of 125 feet above the level of Lake Michigan. There 

 seems to be no doubt but that, by an enlargement of one of the 

 wells to a diameter of 20 inches, a sufficient supply, estimated at 

 17,000,000 gallons per day, could be obtained to meet the de- 

 mands of the city for years to come, and that this would flow into 

 the reservoirs without the aid of expensive engines, steam-pum^ss, 

 and fuel. Another curious feature in regard to these wells, and 

 one which geologists have not 3"et explained, is found in the fact 

 that they are located in no great valley or depression, like the 

 basins of Paris and London, but ai*e out on the level prairie, sur- 

 rounded for hundreds of miles by country of a like character. 

 This fact, taken in connection with the low temperature of the 

 water and the great head of the fountains, seems to indicate that 



