Before the construction of the great sea-dykes in Holland nearly the whole of West Friesland would have been in that hybrid condition described by Pliny in which it was difficult to say whether it belonged to sea or land (_dubiumque terræ sit, an pars maris_). At the present time, however, these lands are richly cultivated and look as if they were a dead level. It is only on close inspection that the monotony is relieved by certain elevations of considerable extent called _Terpen_, whose summits rise to about the level of the larger dykes. These mounds are situated at more or less regular intervals, so that if the tides by any calamity had free scope, they would appear as so many islands scattered over the country. It is on such elevations that modern churches and villages are generally built, and, till they accidentally attracted the attention of agriculturists, nobody seemed to think anything about their origin. A few years ago it was discovered that their interior was composed of a rich ammoniacal deposit which agriculturists found valuable as a fertilising agent when spread over their fields. The excavation of this substance for manuring purposes now forms an important industry, and any landed proprietor who happens to own a workable _terp_--_i.e._ one free of buildings--is on the way to realise a small fortune. When a _terp_ is found suitable for being excavated they generally commence by digging a canal close up to its base, sufficiently large to admit of the passage of good-sized boats. The boats are then easily loaded with the stuff and so it is conveyed to all parts of the country. As the workings advance the canal is also advanced, so that the boats are always in close proximity to the diggings. In the course of these operations, bones and horns of various animals, pottery, and other relics of human industry, were occasionally turned up. By degrees these repeated discoveries attracted the attention of antiquaries, and Dr. Pleyte, of Leyden, is now publishing a large illustrated work on the antiquities of Holland (B. 301), in which a conspicuous place is given to the terp-mounds and their contents. It is, however, to some of the office-bearers of the Museum of the Friesch Genootschap at Leeuwarden, more especially Mr. Corbelijn Battaerd, its conservator, that I am indebted for much of my information on the subject. In this museum are stored up most of the objects hitherto found in the terp-mounds, and the collection, already unique of its kind, is daily and rapidly increasing, as orders have been issued in regard to many of them that no relics are to be disposed of without being, in the first place, submitted to the authorities of the museum.