CATALOGUE. — MAGXETICAL OESERVATIOXS. 



US 



Marine compass. A. P. 1773. 320. 



Lemonnier on removing friction from com- 

 passes. A. P. 1773. 440. H. 1. 



A compass. Roz. Intr. I. 422. 



Lorimer's needle for the dip and the varia- 

 tion. Ph. tr. 1775. 72. 



Cavendish. Ph. tr. 177fi. 375. 



The needle is capable of inversion : the dipping needle on 



Mitchell's construction. 



Gaule's variation compass. A. P. 1777. 

 Krafft on the dipping needle. A. Petr. II. ii. 



170. 

 Ingenhousz on suspending needles. Ph. tr. 



1779. 537. 



Proposes to have them made hollow, so as nearly to float 

 on a fluid, and then suspended by a magnet, with a cavity 

 below to prevent their being shaken off. 



Lac6p^de on compasses, Roz. XV. 140. 

 *Van Swinden on magnetic needles. S. E. 

 VIII. 1780. 



Prize memoir. Proposes flat needles, turning on a pro- 

 jecting point. 



*Coulomb on magnetic needles. S. E. IX. 

 1780. 



Prize memoir.Thinks the form of a needle of little conse- 

 .quencc •. perforating them has scarcely any effect. Divided 

 needles act most powerfully. Found the circle of contact of 

 the needle with its support, in a particular case, -Jj of aline, 

 supposing it to be equally pressed, which is nearly true. 



Coulomb's needle suspended by a thread of 



silk. A. P. 1785.560. 

 Coulomb's mode of measuring the dip, M. 



Inst. IV. 565. B. Soc. Phil. n. 31. 



Compares the weight required to keep the needle hori- 

 2nntal with the time of its horizontal vibration ; and thinks 

 that the dip may be thus determined within lo'or 12'. 



Coulomb. Ph. M. XV. 186. 



Prefers long and broad needles magnetized by Aepinus's 

 method . 



Gattey on guarding needles from electricity, 



Roz. XVII. 296. 

 Rmnouski on observing the dip. A. Petr. 1781. 



V. i. 191. 



E. M. A. VI. 7 14. E. M. PI. V. Marine. III. 

 E. M. Physique. Art. Aimant. Boussole. 



Degaulte sur un compass azimuthal a reflec- 

 tion. 8. R. S. 



Cavallo.Ph.tr. 1786.65. 



Recommends for delicate purposes suspension by a chain 



of horse hair. 



Cotte's variation compass. Roz. XIX. 189. 

 Romans's improved compass. Am. tr. 11.396. 



Repert. IV. 178. 



The box hung on a centre. 



Report on M'Culloch's sea compasses. Lond. 



1788. 

 Drury on cased needles. Ir. tr. 1788. II. IIQ. 



Repert. I. 111. 

 Rennet's suspension of the magnetic needle. 



Ph.tr. 1792.81. Repert. XII. 311. 



Aspider's thread, which, after 1 8000 revolutions, showed 

 no tendency to untwist, and broke at last. 



Prony's instrument for observing the varia- 

 tion. Journ. Phys. XLIV. (II.) 471. 

 Cassini's azimuth compass. M, Inst, V. 145. 



Magnetical Observations. 



Howard on a reversion of the needle. Ph. Ir. 



1676. XI. 647. 

 Reversion of a compass. Ph. tr. 1684, XIV, 



520. 

 Middleton. Ph. tr. 1738. XL. 310. 



Found the needle afiected by cold so that it could not 

 traverse. 



Bouguer on marine observations of declina- 

 tion. A. P. Pri.x. II. vi. 



Remark on the disturbance of the nee'dle by 

 the electricity of the glass. Ph. tr. 1746. 

 XLIV. 242. ' 

 The electricity may be removed by a wet finger. 



Waddel and Knight on the destruction of 

 polarity by lightning. Ph, tr, J749. XLVI. 

 111. 



