The following extracts from the report of the Hon. John Flannagan, United States Consul at Bruges, in Belgium, to the Secretary of State, published in the Washington City _Telegraph_ of a late date, will fully explain what is meant by the "Great Scare in Belgium." Our extracts are not taken continuously, as the entire document would be too voluminous for our pages. But where breaks appear we have indicated the hiatus in the usual manner by asterisks, or by brief explanations. GEN. FLANNAGAN'S REPORT. BRUGES, December 12, 1872. To THE HON. HAMILTON FISH, Secretary of State. SIR: In pursuance of special instructions recently received from Washington (containing inclosures from Prof. Henry of the Smithsonian Institute, and Prof. Lovering of Harvard), I proceeded on Wednesday last to the scene of operations at the "International Exploring Works," and beg leave to submit the following circumstantial report: Before proceeding to detail the actual state of affairs at Dudzeele, near the line of canal connecting Bruges with the North Sea, it may not be out of place to furnish a succinct history of the origin of the explorations out of which the present alarming events have arisen. It will be remembered by the State Department that during the short interregnum of the provisional government of France, under Lamartine and Cavaignac, in 1848, a proposition was submitted by France to the governments of the United States, Great Britain and Russia, and which was subsequently extended to King Leopold of Belgium, to create an "International Board for Subterranean Exploration" in furtherance of science, and in order, primarily, to test the truth of the theory of igneous central fusion, first propounded by Leibnitz, and afterward embraced by most of contemporary geologists; but also with the further objects of ascertaining the magnetic condition of the earth's crust, the variations of the needle at great depths, and finally to set at rest the doubts of some of the English mineralogists concerning the permanency of the coal measures, about which considerable alarm had been felt in all the manufacturing centers of Europe. The protocol of a quintuple treaty was finally drawn by Prof. Henry, of the Smithsonian Institute, and approved by Sir Roderick Murchison, at that time President of the Royal Society of Great Britain. To this project Arago lent the weight of his great name, and Nesselrode affixed the approval of Russia, it being one of the last official acts performed by that veteran statesman.