258 ^^ '^^^ ELECTRIC COLUMN. 



are also the effects of a particular fluid, but that its func- 

 tions in nature are not confined to those of attracting or 

 repulsing iron according to circumstances, and producing 

 in a movable needle the property of keeping more or less 

 ^ parallel to the meridian of the place, with a determined 

 end pointing towards the north; though the latter, by its 

 use in navigation, is become of great importance. 

 Its phenomena With respect to this astonishing phenomenon. Prof. Van 

 VarSwinden. Swinden of Franeker has much advanced what Bacon calls 

 ihe^History '\\\ every class of phenomena, by an indefatigable 

 perseverance in observing the variations of the magnetic 

 needle compared with various circumstances. This, for 

 every phenomenon, is the first step toward the discovery of 

 causes; for the nature of those that may be devised must 

 answer to all the modifications of the phenomena carefully 

 observed, before confidence can be granted to any hypo* 

 thesis. 

 Its polarity In magnetism, the main point which must direct the 



be studiedf natural philosopher in search of a cause is the same which 

 directs the navigator, namely the direction of the magnetic 

 needle; for this must belong to a cause, which in some 

 manner influences the whole Earth. This consideration has 

 suggested to Prof. Prevost of Geneva an idea, which, 

 though not completed, deserves notice. After all the dis- 

 coveries already made in meteorology and chemistry, it 

 Light proba- cannot be doubted, that light has, in various ways, a great 

 bly concerned gij^j-g [^ jj^g formation of many atmospheric fluids, and thus 

 probably of the magnetic : but there must be some cause 

 of the formation of a greater quantity of it on the northern 

 than the southern hemisphere of the Earth, since the 

 magnetic needle has a tendency to turn that way. T shall 

 not enter into particulars on Mr. Prevost's hypothesis, and 

 shall only mention its ground, in order to show, that this 

 object may not be unattainable; it is the circumstance, that 

 the sun remains about 8 days longeron the northern side of 

 the ecliptic, than on the southern. 

 Saussure'si With respect to phenomena which may indicate a forina- 



ter* ^'O" of this fluid, Mr. de Saussure has invented a very im- 



portant instrument, which he has called magnetometer ; 

 showing variations in tlie intensity of attraction of a magnei 



m 



