234 Ow the Effect of Quantity of Matter in 



the last position of the bar and the microscopes remain mi- 

 disturbed in their position until morning. The arrangement 

 of the boxes in which the bars are contained and the mechan- 

 ism of the movements appear to me very well planned. 



From what little I have quoted, it may be easily seen, that 

 the paper of Mr. H. deserves the attention of those who take 

 an interest in the mechanical arrangements necessary in 

 practical astronomy and geodesy. It is to be lamented, 

 that such a complete apparatus as that now on hand in 

 America, has not been applied according to its intention 

 and by its author. (Signed,) F. W. Bessel. 



Art. III. — On the Effect of Quantity of Matter in Modify- 

 ing ths Force of Chemical Attraction; by Elisha Mitch- 

 ell, Professor of Chemistry, Mineralogy, and Geology, in 

 the University of North Carolina. 



In my present communication to the Journal, I do not pro- 

 pose to bring forward any new fact or argument. With 

 reference to the subject of which it treats, both have already 

 been sufficiently multiplied. My object is merely to call the 

 attention of chemists, to some facts that appear to have been 

 unaccountably neglected, and to correct mistakes respecting 

 others, which have found their way into books of the greatest 

 authority. 



It is stated, in substance, in our treatises of chemistry, that 

 the force of chemical attraction is modified by the quantity 

 of matter by which it is exerted, and in some of them, the 

 opinion is advanced, that quantity of matter may in some 

 cases, compensate for a weaker affinity. But the statement 

 is generally made in such a way, and accompanied by so 

 many qualifications and expressions of doubt and hesitation, 

 that it appears like a reluctant admission of a disagreeable 

 truth rather than a free and willing enunciation of a law of 

 nature. The following extract from one of the best of our 

 elementary books, may serve for illustration. 



"Though this mode of determining the relative forces of 

 affinity, cannot be admitted, it is possible that quantity of 

 matter, may some how or other, compensate for a weaker af- 

 finity, and Berthollet attempts to prove it by experiment. 

 On boiling the sulphate of baryta, with an equal weight of 

 pure potash, the alkali is found to have deprived the baryta 



