7i6 



THE POPULAR SCIENCE MONTHLY. 



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 18S3 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 Berliu, 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 contain- 

 ing an excess of salts. After four months 

 of 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 

 lirae-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 Archi- 

 bald Geikie goes back to the time when it 

 was not yet an island, but formed a part of 

 the European Continent. Its separation oc- 

 curred 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 immi- 

 grants may have made their way." It was 

 probably finally washed away as much as 

 sunlc. At the dawn of history, the general 

 appearance of the country must have been 

 characterized by wide-spread forests, abun- 

 dant 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 every- 

 where were the resorts of broken and des- 

 perate 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 

 copsewood. Great topographical changes 

 have been wrought by the disappearance of 

 the fens and bogs. Some have been natu- 

 rally silted up, and others have been arti- 

 ficially drained ; while 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 ex- 

 amination 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 at- 

 tention in the United States. Their prog- 

 ress is much more rapid than any one could 

 suppose till he begins to make it the sub- 

 ject of careful observation. 



The Rnby-Mincs of Bnrmah. — 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 com- 

 posed 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 trav- 

 ersed 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 pres- 

 ent 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 



