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THE POPULAR SCIENCE MONTHLY. 



as much impurity. " From data gathered by 

 me," says Dr. Hunt, " and published some 

 years since in a ' Report of the Geological 

 Survey of Canada,' it appears that the amount 

 of foreign matters in Turk's Island salt is 

 2.34 ; in Saginaw salt, 2.00 ; in Syracuse 

 solar salt, 1.15 ; and in the boiled salt from 

 the same locality about 1.50 per cent. Of 

 the salt made at Goderich from the brines 

 pumped from the salt-bearing strata of the 

 region, three samples, analyzed by me in 

 1871, gave: for coarsely crystalline salt) 

 1.097 ; flaky medium salt, 1.282 ; and fine 

 salt, 1.625 per cent, of foreign impurities. 

 The fine salt, which is the least pure, is 

 made by boiling, the others by slower evap- 

 oration. The analysis by Dr. Goessmanu of 

 another sample of Goderich boiled salt gave 

 1.50 ; while the rock-salt from the layer of 

 10| feet in Division VIII. of the section 

 [the twenty-five-foot layer mentioned above] 

 contains only 0.234 per cent., or less than 

 one-sixth of the amount of foreign matter 

 found in the boiled salt made from the 

 Goderich brines." 



ibont the English Sparrow. A spirited 

 but entirely courteous controvei'sy is being 

 carried on in the columns of our contem- 

 porary. Forest and Stream, about the English 

 sparrow. The principal questions in dis- 

 pute are whether this bird is useful as a 

 destroyer of noxious insects, worms, and the 

 like, and whether it banishes from its 

 haunts all other species of small birds. 

 The evidence is conflicting. Some of the 

 writers say of the sparrows that they are 

 " exceedingly quarrelsome among them- 

 selves," and intolerant of birds of a differ- 

 ent species. When a stranger-bird makes 

 his appearance among them, the fury of the 

 whole sparrow community is turned upon 

 him ; they chase him hither and thither, 

 giving him no rest until he is banished from 

 the ncighborliood. " They " (the sparrows) 

 " let the orchards go to ruin," we are told, 

 " for they will not cat every kind of insect." 

 One writer sums up the case against the 

 sparrows thus : 1. They have no personal 

 attractions except their tameuess ; 2. They 

 are practically useless ; they may have been 

 useful on their first arrival from Europe, but 

 they are too much pampered to be so now ; 

 3. They destroy fruit-blossoms ; 4. They 



are often quarrelsome, and sometimes drive 

 away useful birds. On the other hand, we 

 are told that the sparrows destroy immense 

 numbers of larvae, especially during the 

 winter ; that they are not hostile to other 

 birds ; that they do not destroy fruit-germs. 

 A writer who lives in Tenafly, New Jersey, 

 says : " We have a few sparrows in the 

 yard, and find their presence makes very 

 little difference with the other birds. We 

 have sixteen varieties of birds in the yard 

 at this writing, viz., brown thrush, robins, 

 catbirds, orioles, wood - robin, bluebirds, 

 phoebe-bird, cuckoo, kingbird, and the rest 

 warblers of different kinds. We find the 

 most quarrelsome to be the kingbird and 

 black oriole. These last are chasing almost 

 everything that crosses their path." 



Hygiene of the Eyes. A series of ques- 

 tions touching the care of the eyes were 

 recently submitted to Dr. E. G. Loriug, Jr., 

 by the Medico-Legal Society of New York. 

 Dr. Loring replied in a paper which has 

 since been published in tlie Medical Eecord. 

 To the first question namely, whether bad 

 air has any direct effect on the sight ? the 

 author replies that vitiated air has a spe- 

 cially irritating influence on the mucous 

 membrane of the eye ; and that bad air, as 

 a primal cause, may set in train morbid 

 processes which not only will affect the 

 working capacity and integrity of the or- 

 gan, but may even lead to its total destruc- 

 tion. The second question was, whether 

 size and quality of type may cause disease 

 of the eye ? According to Dr. Loring, the 

 smallest print which a normal eye can read- 

 ily recognize at a distance of one foot is 

 about /y inch, and at eighteen inches' dis- 

 tance about 3^- inch. The normal eye 

 should never be subjected for any length of 

 time to a type smaller than twice this size, 

 or -,\ inch, and it would be better, after 

 middle-life, to employ a type even a little 

 larger than this ; but the employment of 

 spectacles removes in a great degree the 

 necessity of a larger type with advancing 

 years. The finer the type, the closer the 

 book has to be held to the eye, and the 

 greater the demand on the focalizing power 

 and the muscles that bring both eyes to 

 bear at once upon the print. On the other 

 hand, too coarse type is wearisome to the 



