British Rainfall 1867, p.8
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British Rainfall 1867 page 8
 a truly vertical position. At the lower end is a small mirror, (D), turning on a horizontal axle, whereof one end is prolonged at (E), and carries a pointer on the graduated arc (AB). If the mirror is (as represented) at an angle of 45°, objects level with the mirror will be seen in its middle, by looking through the small eye-hole at the top; but, if objects are above its level, the mirror must be turned by the axle (E) into a more horizontal position, and when the objects are seen crossing the centre of the mirror, the index will be found as many degrees towards (A) as the objects are above the instrument. It is, perhaps only fair to state that Mr. Pastorelli, of Piccadilly, has turned out the altameter in his usual satisfactory manner, and that those who have seen it, approve its simplicity, and the apparent impossibility of error. ALTITUDE ABOVE SEA LEVEL. AMONG the many difficulties of preparing the general tables at the end of this work, not the least has been to ascertain the altitude of the various stations above the level of the sea. Although, perhaps, there are few parishes which have not been levelled through, either for road, rail, drainage, or canal works, yet the results are often destined to interment in the drawers of engineers, and ultimately to destruction, as waste paper. The levels of the Ordnance Survey are almost the only ones available for general use, and to their datum (the mean level of the sea at Liverpool) all are now referred. But, except in the Northern Counties, and along certain main roads, their levels are untaken, or, at any rate unpublished, 'though under the guidance of Captain Edward James, R.E., they are being pushed steadily forward. There are still however large tracts in which no levels have been taken (e.g. Bury St. Edmunds, 15 miles from the nearest bench mark), and, for the use of observers in such districts, arrangements were made last spring for a ten day series of simultaneous barometer readings, the returns being sent to me; and the approximate altitude of the stations therefrom deduced have materially helped to extend our knowledge in this respect. Further assistance was afforded by the offer (in the Meteorological Magazine) of information, so far as lay in my power, as to the altitude of churches, or other prominent |
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