808 DISCOURSE ON THE STUDY 



sist in observed relations among the data of physics, 

 which show them to be quantities not arbitrarily 

 assumed, but depending on laws and causes which 

 they may be the means of at length disclosing. 

 A remarkable instance of such a relation is the 

 curious law which Bode observed to obtain in the 

 progression of the magnitudes of the several planet- 

 ary orbits. This law was interrupted between Mars 

 and Jupiter, so as to induce him to consider a 

 planet as wanting in that interval; a deficiency 

 long afterwards strangely supplied by the discovery 

 of four new planets in that very interval, all of 

 whose orbits conform in dimension to the law in 

 question, within such moderate limits of error as 

 may be due to causes independent of those on which 

 the law itself ultimately rests.* 



(34&.) Neither is it irrelevant to our subject to 

 remark, that the progress which has been made in 

 this department of chemistry, and the considerable 

 exactness actually attainable in chemical analysis, 

 have been owing, in great measure, to a circum- 

 stance which might at first have been hardly con- 

 sidered likely to exercise much influence on the 

 progress of a science, the discovery of platina. 

 Without the resources placed at the ready disposal 

 of chemists by this invaluable metal, it is difficult to 

 conceive that the multitude of delicate analytical 

 experiments which have been required to construct 

 the fabric of existing knowledge could have ever 

 been performed. This, among many such lessons, 



* The progress of astronomical discovery has since shown 

 that this law cannot be relied on (1851). 



