147 
In his article on ‘‘Magnetism,’’ published in the Axcyclopedia 
Britannica, Professor Chrystalsays: ‘‘ The notion of molecular mag- 
nets seems to have been suggested by Kirwan ; but it was not until a 
definite form was given to it by Weber that it acquired any impor- 
tance.’’ The views of Kirwan here referred to are contained in 
a paper entitled ‘‘ Thoughts on Magnetism,’’ published in the 
Transactions of the Royal Irish Academy for 1797. In this paper 
Kirwan states as follows: ‘‘ A magnet therefore is a mass of iron or 
of iron ore, whose oxygenation does not exceed twenty per cent. or 
thereabouts, whose particles are arranged in a direction similar to 
that of the great internal central magnets of the globe. ‘This I call 
the magnetic arrangement. .... Hence a magnet attracts tron 
when within the sphere of its action by forcing, in virtue of its at- 
tractive power, a certain proportion of its integrant particles into a 
disposition and arrangement similar to that of its own..... 
The disposition of parts in a particular magnet, being similar to 
that which obtains in the great internal general magnet, extends in 
the direction of from north to south. Hence magnets, when 
at liberty to move with a certain degree of freedom, and iron 
when a sufficient number of its particles are arranged in that 
direction, and has sufficient liberty to conform to it, points to those 
poles. Hence this property is called polarity. .... The mag- 
netic power is greater or lesser according to the number and homo- 
geneity of the particles s¢m/arly and magnetically arranged. ... . 
The power of a magnet (everything else being equal) depends on 
the number of its surfaces magnetically arranged and the accuracy 
of that arrangement. ... ... The arrangement is accurate when 
the synonymous surfaces are exactly parallel to each other and 
originally conformed to and parallel with those of the great 
general magnet. . . . . Amy motion communicated to the integrant 
particles of iron placed in a proper situation helps them to assume 
the magnetic disposition already impressed upon them by the great 
general magnet.’’* 
These quotations from Kirwan’s paper appear to show that 
the views he held on the nature of magnetism were vague and in- 
definite ; and therefore seem to justify Prof. Chrystal’s conclusion 
that the molecular theory in the form proposed by Kirwan did not 
acquire any importance. Especially would this be so in view 
of the fact that in 1600 Gilbert, in his book ‘‘ De Magnete,”’ 
* Trans. Royal Irish Acad., vi, 177, 1797. 
