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by Prof. Lamont, Mr. Lloyd said that, as respects certain 

 instruments intended for observations of a particular kind, 

 there seemed now to be a pretty general agreement on the 

 subject. He had himself proposed an instrument for the de- 

 termination of the changes of the Magnetic Inclination, in 

 which the magnet was necessarily a small one ; and the ad- 

 vantages of small magnets, in the delicate observation of 

 the absolute Horizontal Intensity, seemed now to be fully 

 recognized. 



While engaged in considering the best form of an instru- 

 ment intended for observations of the latter class, Mr. Lloyd 

 was led to perceive, that the same apparatus might be made 

 to serve also in the determination of the Absolute Declina- 

 tion;* and, by a few slight additions in the details of its 

 construction, in that of the variations of the three magnetic 

 elements. It may likewise be employed for all the usual pur- 

 poses of a Theodolite ; and thus, with the addition of an or- 

 dinary Inclinometer, a Chronometer, and a Sextant, consti- 

 tute a complete magnetical equipment for the use of the tra- 

 velling observer. 



The following is a brief description of the instrument. 



A divided circle, similar to that of a Theodolite, is sup- 

 ported on a tripod base, with levelhng screws. This circle is 

 nine inchesf in diameter; it is divided to 10', and subdivided 

 by two verniers to 10". The upper plate of the circle has two| 

 projecting arms, each carrying a pair of adjustable Y sup- 

 ports for the reading telescope, at a distance of six inches from 

 the centre. The telescope rests in these supports on a tran- 



* It may be proper to observe that this arrangement had occurred to the writer 

 before he had seen Prof. Lamont's account of his magnetical Theodolite, an instru- 

 ment in which the same end is obtained, although by different means. 



f A circle six inches in diameter, and read to 20", is suflScient for all the pur- 

 poses of a travelling observer. 



X One is sufficient, and the instrument will be so modified in all future construt- 

 tions on the same plan. 



