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of Medicine in the United States and Canada. Pp. 

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Romanes, G. J. Mental Evolution in Man. New 

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Serviss, Garrett P. Solar and Planetary Evolu- 

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 24. 10 cents. 



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Smith, Charles Lee. History of Education in 

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Stowe, Winthrop E. Investigations concerning 

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 Tenn. Pp. 26. 



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 London and New York: Longmans, Green & Co. 

 Pp. 161. 



Thwing, Edward P., M. D. Euthanasia In Ar- 

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Tuckernian, Frederick, M. D. The Gustatory 

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POPULAR MISCELLANY. 



Natnral Purification of Polluted Streams. 



— The growing population of the many cities 

 which discharge their sewage into rivers gives 

 increasing importance to the question how 

 great a degree of pollution is allowable in a 

 stream of given flow, the water of which is 

 to be used lower down for domestic or for 

 manufacturing purposes. Mr. Rudolph Ber- 

 ing says that oxidation and decomposition of 

 sewage matter was for a long time thought 

 to be the main cause for the clarification of 

 polluted rivers. To-day it is known to be 

 but a minor cause compared with dilution 

 and subsidence ; and if the sewage is dis- 

 charged in a fresh condition into a stream of 

 water, its destruction is in part due to fish 

 and other aquatic animals. Some of the ref- 

 use from stock-yards is disposed of, no doubt, 

 in this way. Most of the decomposition, or 



oxidation as it is usually termed, of sewage 

 is effected by the myriads of microscopic 

 plants, microbes, or bacteria contained in 

 both air and water, which at once seize upon 

 the dead organic matter. For purifying the 

 sewage discharged into a river, oxidation can 

 be depended upon only to a limited extent, 

 because of the comparative slowness with 

 which it takes place. Subsidence of the 

 heavier matter tends to clarify it before it 

 flows many miles ; dilution with a sufiicient 

 quantity of clean water prevents an offen- 

 siveness almost at once ; but oxidation re- 

 quires many days under continuous aeration 

 of the river. From a comparison of data in 

 regard to the actual purification of polluted 

 streams we may draw the following infer- 

 ence : Rivers not to be used for water-sup- 

 plies, but to be inoffensive to communities , 

 residing a few miles below, to remain fit for 

 ordinary manufafcturing purposes, and to sus- 

 tain the life of fish, may receive the sewage 

 from one thousand persons for at least every 

 one hundred and fifty to two hundred cubic 

 feet of minimum flow per minute, supposing 

 that natural subsidence of the heavier mat- 

 ter takes place immediately below the town 

 discharging the sewage. Beyond the above 

 limit it appears to be advisable to resort to 

 land or other filtration, or to chemical pre- 

 cipitation. But the whole subject needs 

 further investigation. 



The Nebraska City Pontoon Bridge.— 



Colonel S. N. Stewart, of Philadelphia, has 

 recently built a pontoon bridge for ordinary 

 traSic across the Missouri River, at Nebraska 

 City. It is 1,07-1 feet long, 24^ feet wide, 

 and consists of a flooring laid upon boats 

 which float upon the river and are securely 

 anchored. The city has held a franchise for 

 such a bridge for twelve years, but the pro- 

 ject has been opposed by persons interested 

 in steamboats plying on the river. Many 

 predicted that the attempt would fail, for 

 the Missouri River has a swift current, which 

 here attains about its highest velocity, and 

 large numbers of logs and trees are constant- 

 ly drifting in the stream. These, however, 

 are carried under the floats without doing 

 any damage. In the channel of the river the 

 bridge makes a V, pointing down stream, 

 which is the draw. To open the draw, the 

 connections at the point of the V are cast 



