ments. In all the wars of other powers Belgium has maintained a strict neutrality. In the Franco-Prussian war of 1870 she forbade the sale of war munitions to either of the contending parties, and disarmed and interned all soldiers of either army that entered her territory. Her peace was seriously threatened at one time during that war, but was saved through the conclusion of a triple treaty between England, France, and Prussia, by which the independence and neutrality of Belgium were guaranteed under the terms of the treaty of 1839.
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For nearly fifteen years following the siege of Antwerp and the establishment of Belgium as an independent kingdom the general peace of Europe and America continued. Spain suffered to some extent from civil war; Don Carlos in April, 1833, declared himself the legitimate successor to the king, and the result was the Carlist war of that period, which continued with varying fortunes until the final overthrow of the pretender in 1839. In 1840, and the three succeeding years, there were various revolutionary movements in Spain, most of them resulting in bloodshed and some in hostilities of considerable magnitude, but in the final result the succession to the throne was not disturbed, and Spain suffered no loss, or made no increase, of territory.
Russia was at peace with her European neighbors. Her impatient eyes were fixed upon Asia, and in 1839-40, she sent an expedition for the conquest of Khiva. It had a disastrous result, and for more than thirty years thereafter Khiva retained her independence in the midst of the desert sands of Central Asia.
In 1835 began the "opium war" between China and England, growing out of the proclamation of the Chinese emperor prohibiting the importation of the pernicious drug into his dominions. Opium was the chief source of revenue of the British in India, and consequently Eng-
