Page:Popular Science Monthly Volume 1.djvu/262

250 done with pulverized charcoal, or gunpowder. Then the instrument with which this man was tattooed, and which he brought away with him, is split like a steel pen at the tip, so that fluid substances could easily be taken up by it.

, of the Edinburgh College of Physicians, says of idiocy and its relations to marriages of consanguinity, that in more than sixty per cent, of the cases of idiocy occurring in the British Isles the condition is acquired, not congenital, and is due to one or other of the numerous accidents to which children are liable. He disapproves of unions of near relations, but states that proof is wanting that any evil resulting from them is dependent on a mysterious influence intrinsic in the consanguinity itself. His objections to marriages of blood-relations proceed rather from a consideration of the increased risk in such unions of the transmission of morbid peculiarities. Thus, if a deaf-mute is married to a person in possession of the faculties of speech and hearing, the chances of having a deaf-mute child will be as 1 to 135; but, if deaf-mutes intermarry, the chances of having a deaf-mute child rise to 1 in 20.

Speaking of the causes which produce idiocy after birth, Dr. Mitchell points out that purely intellectual exercise, in excess, is more detrimental to children than purely emotional exercise in excess, but the reverse holds true in the case of adults. In children as well as in grown-up persons, disorder of the moral faculty, as a rule, precedes intellectual disorder, and overteaching of pupils is first apparent in change of character. Prolific causes of idiocy are scarlet fever, whooping-cough, and measles, diseases to which thirty per cent, of all the idiots and imbeciles in Great Britain are due.

In its provisions for securing to consumers a sufficient supply of pure water, the public health bill, now before the English Parliament, thus defines what will be considered as polluting liquids:

1. Any liquid containing in suspension more than three parts by weight of dry mineral matter, or one part by weight of dry organic matter, in 100,000 parts by weight of the liquid.

2. Any liquid containing in solution more than two parts by weight of organic carbon, 1, or .03 by weight of organic nitrogen, in 100,000 parts by weight of the liquid.

3. Any liquid which exhibits by daylight a distinct color, when a stratum of it 1 inch deep is placed in a white porcelain or earthenware vessel.

4. Any liquid which contains a solution, in 100,000 parts by weight, more than two parts by weight of any metal except calcium, magnesium, potassium, and sodium.

5. Any liquid which, in 100,000 parts by weight, contains, whether in solution or suspension, in chemical combination or otherwise, more than .05 part by weight of metallic arsenic.

6. Any liquid which, after acidification with sulphuric acid, contains, in 100,000 parts by weight, more than one part by weight of free chlorine.

7. Any liquid which contains, in 100,000 parts by weight, more than one part by weight of sulphur, in the condition either of sulphuretted hydrogen or of a soluble sulphuret.

8. Any liquid possessing an acidity greater than that which is produced by adding two parts by weight of real muriatic acid to 1,000 parts by weight of distilled water; or—

9. Any liquid possessing an alkalinity greater than that produced by adding one part by weight of dry caustic soda to 1,000 parts by weight of distilled water.

The difficulty with photographs is, that they fade; the desideratum is to give them stability. Mr. W. H. Sherman, of Milwaukee, has been experimenting for some time past with a view to this object, and claims to have reached the result sought. The object was to introduce an unchangeable pigment of some kind into the print by deposition from solution, and he succeeds with the bisulphide of mercury (vermilion). The process and its explanation are as follows: "A solution is prepared, composed