ON MAGNETICAL AND METEOROLOGICAL OBSERVATIONS. 9 



the construction and adjustments of this instrument are given in the work 

 cited below. 



Weber's Inductive Inclinometer. — Similar in respect of its general principle, 

 but widely different in the mode of application of that principle, is a recent 

 invention of M. Weber for the same purpose. The deflection of the horizontal 

 magnet in this instrument is produced by the earth's magnetism, induced not 

 on a vertical soft iron bar at rest, but on a ring, sphere, or plate of copper 

 made to revolve about a vertical axis with a perfectly uniform and given ve- 

 locity by clockwork. This ingenious instrument has not been tried in Eng- 

 land, but is stated by M. Kupffer to perform very satisfactorily. 



M. Lamonts Inclinometer. — A third and much less simple mode of ac- 

 complishing the same object of measuring the intensity of the earth's mag- 

 netism by its inductive power has been devised by M. Lamont. As in Dr. 

 Lloyd's process, a bar of soft iron is used as the temporary magnet, but in 

 other respects the application of the general principle is widely different. 

 The bar so temporarily magnetized is made to act unequally on the two 

 bars of an astatic magnetic couple, thereby tending to draw them aside from 

 a given position in which they would otherwise be held by a fixed magnet of 

 given power. This tendency however is destroyed by another magnet placed 

 in a given position and distance. A series of reversals and changes of di- 

 stance in the soft iron bar and the neutralizing magnet is then operated, which 

 furnishes equations by which everything but the intensity sought and known 

 quantities can be eliminated. 



7. Publication of Magnetic Observations, Descriptions of Observatories, fyc. 



As it is not by any means the object of this Report to give a historical 

 view of the progress of magnetic science generally, except in so far as the 

 immediate purposes for which your Committee is constituted are concerned, 

 and as bearing on the practical operations over which they are delegated by 

 the Association to watch, — it must suffice under this head to notice very 

 briefly the appearance of several works and memoirs, in which observations 

 are recorded or discussed, instruments and observatories described, &c. 



None of the returns of the regular observations at our stations are as yet 

 printed ; but, as has been noticed, those of the disturbances in 1840 and 1841 

 will appear in the course of the present year. In this respect however we 

 are not more in arrear than our Russian coadjutors, the observations made 

 in the whole extent of which empire under the superintendence of M. 

 Kupffer, for the year 1839, have appeared in the course of 1841, forming the 

 regular continuation of that noble collection, the " Annuaire Magnetique et 

 Meteorologique du Corps des Ingenieurs des Mines de Russie". Nor indeed 

 does it seem practicable in works of this vast extent, and where the returns 

 have to arrive from such distant quarters, to place a much less interval be- 

 tween the making and publication of the ordinary observations. 



The year elapsed has also been marked by the publication of the first vo- 

 lume of the magnetic and meteorological observations made at Prague by M. 

 Kreil, containing the observations from July 1, 1839 to July 1, 1840; a sin- 

 gular departure from the usual and far more convenient practice of packing 

 together in the same volume the observations of each separate year. In this 

 work the observations are not only registered, but very amply discussed and 

 reduced, and the daily, monthly, and yearly march of the results investigated. 

 The suspected influence of the moon on magnetic and meteorological phse- 

 nomena is made a subject of especial discussion by M. Kreil. 



M. Quetelet continues his praiseworthy labours in collecting and project- 

 ing meteorological observations on the solstitial and equinoxial term days. 



