142 PHILOSOPHICAL TRANSACTIONS. [aNNO 1792. 



under the torrid zone are cooled by a contact with its waters, and in return, the 

 breezes from the sea, which, at certain hours of the day, come in to the shores 

 in almost all hot countries, bring with them refreshment, and, as it were, new 

 life and vigour both to the animal and vegetable creation, fainting and melting 

 under the excessive heats of a burning sun. What a vast tract of country, now 

 the most fertile on the face of the globe, would be absolutely barren and unin- 

 habitable on account of the excessive heat, were it not for these refreshing sea 

 breezes. And is it not more than probable, that the extremes of heat and of 

 cold in the different seasons in the temperate and frigid zones would be quite in- 

 tolerable, were it not for the influence of the occim in preserving an equability 

 of temperature? 



To these purposes the ocean is wonderfully well adapted, not only on account 

 of the greater power of water to absorb heat, and the vast depth and extent of 

 the different seas (which are such that one summer or one winter could hardly 

 be supposed to have any sensible effect in heating or cooling this enormous mass;) 

 but also on account of the continual circulation which is carried on in the ocean 

 itself, by means of the currents which prevail in it. The waters under the 

 torrid zone being carried by these currents towards the polar regions, are there 

 cooled by a contact with the cold winds, and, having thus communicated their 

 heat to these inhospitable regions, return towards the equator, carrying with 

 them refreshment for those parching climates. 



V. A New Suspension of the Magnetic Needle, intended for the Discovery of Mi- 

 nute Quantities of Magnetic Altraction; also an Air T^ane of great Sensibility; 

 with New Experiments on the Magnetism of Iron Filings and Brass. By the 

 Rev. A. Bennet, F. R.S. p. 81. 



To manifest the various degrees of attraction between magnets and ferrugi- 

 nous bodies, different methods have been used. The substance to be tried has 

 either been simply brought into contact with the magnet, or has been made to 

 float on water or mercury. Needles are commonly made to rest horizontally on 

 sharp-pointed wires, and as an improvement on these methods, Mr. Cavallo has 

 suspended a needle by a chain of horse-hair, consisting of 5 or 6 links, which 

 move very freely in each other, and allow the needle to turn more than a whole 

 revolution round its centre. Others have suspended the needle by fine threads, 

 or silk; but as these, on turning round a few times, will cause the needle to 

 deviate from its meridian by twisting, they are certainly objectionable. 



After considering each of the above methods, and trying some of them, Mr. 

 B. suspended a small sewing needle, by means of a sj)ider's thread, in the cylin- 

 drical glass of his gold-leaf electrometer; and having satisfactorily proved its mag- 



