THE ROARING FORTIES 139 



was accepted as normal and inevitable. The 

 addition of 12,000,000 square miles of territory 

 to their 18,000,000 aroused no misgivings in the 

 mass of the people, and there were not lacking 

 those who felt that the whole of Mexico should 

 properly have been taken over instead of the 

 northern provinces only. In the very month 

 in which the treaty of peace was signed (Feb 

 ruary, 1848), by one of the most astonishing 

 coincidences that history records, the acquisi 

 tion of California was justified, in the economic 

 sense, by the discovery of gold in its mountains. 

 As against this providential confirmation of 

 manifest destiny, promptly developed the bitter 

 strife over slavery in the new territory, with 

 results so disastrous to the unity of the nation. 



Between 1815 and 1840 the population of 

 the United States increased from 8,000,000 to 

 17,000,000. While large, this gain was not 

 astounding, and it certainly gave no basis for 

 an extension of territory. Overcrowding could 

 not be considered imminent when the number 

 of persons per square mile stood at 9.73. As 

 compared with the United Kingdom the growth 

 of the United States had effected a significant 

 change in relations. The War of 1812 was 

 fought by a people numbering 8,000,000 against 



