Page:Popular Science Monthly Volume 32.djvu/736

716 vesicle, the same as it might any other wound. According to statistics presented by Dr. Buchanan, the proportion of such accidents that occurred in England and Wales during 1883 was 51 infants dying of septic disease out of 763,192 vaccinated.

Lime-Salts in the Food and the Teeth.—Dr. W. D. Miller, of Berlin, has been making experiments to determine how far changes can be produced in teeth by the presence or absence of lime-salts in food. His method is to extract a tooth from a healthy dog, and then to feed the animal upon food containing but little lime-salts for three months; then to remove a second tooth, and change the food to one containing an excess of salts. After four months o-f this treatment another tooth is extracted. The author has found that an appreciable loss of lime-salts occurs in the first stage, which amounts in one case to more than one per cent, and that the proportion of lime-salts rises again to normal during the second stage.

The Making of Britain.—In studying, by geological evidences, the changes which have taken place in Great Britain since it was first inhabited by man, Professor Archibald Geikie goes back to the time when it was not yet an island, but formed a part of the European Continent. Its separation occurred by gradual subsidence, in which the chalk ridge between Dover and Calais was the last landmark to disappear; and "along this narrow ridge the earliest Celtic immigrants may have made their way." It was probably finally washed away as much as sunk. At the dawn of history, the general appearance of the country must have been characterized by wide-spread forests, abundant bogs and fens, and a profusion of lakes; and at the first coming of the Romans the greater part of the country was probably covered with wood. Large tracts of these woods persisted for many hundred years, and as late as the twelfth century the woods to the north of London swarmed with wild boars and wild oxen, and the woods everywhere were the resorts of broken and desperate men. In the course of generations the wood and open land have largely changed places. The belts of clay soil, originally the most heavily timbered tracts, proved admirably adapted to agricultural purposes and were cleared for cultivation, while the open places, with their light soils, were abandoned, to become wastes of scrub and copse wood. Great topographical changes have been wrought by the disappearance of the fens and bogs. Some have been naturally silted up, and others have been artificially drained; which their sites are still indicated by such Saxon names as Bogside, Bogend, and Mossflats; and by the black, peaty soil which marks where they once lay. No one would be led to suspect by the examination of modern maps the number of lakes that once dotted the north of England and Scotland; but inspection of old maps will show many sheets of water that do not now exist, or are much reduced in size. Topographical names will reveal the sites of other and sometimes still older lakes, while geological evidence will tell of others of which there is no human record. Other changes have been and are going on along the shore, where the land is washed away at some places and added to at others. All these things are subjects for profitable study, and call for it; and we may add that similar changes are going on and invite attention in the United States. Their progress is much more rapid than any one could suppose till he begins to make it the subject of careful observation.

The Ruby-Mines of Burmah.—The ruby-mine tract in Burmah, according to Mr. G. Skelton Streeter's description in the British Association, is a large valley some twelve miles long by eight miles broad, and composed of several small valleys, or rather basins. It lies on the slope of the Sibwee Doung, which divides the Irrawaddy and Salwen Rivers. The valley bears signs of volcanic origin. The mines are of three distinct kinds. The first is furnished by the metamorphic rock, whose mass is traversed in all directions by huge fissures, caused probably in the past by shrinkage. These fissures are filled with a soft, clayey earth, generally containing rubies. At present they are worked in a very superficial manner. The mines of the second variety are on the sides of these rocky hills, where diversified strata of clayey consistency have