4">1 Prof. Young's Concise Method of determining 



. Now, it has been a long- and well-established fact in Corn- 

 wall, that metalliferous and other veins continue their course 

 uninterruptedly through both the granite and the slate ; that 

 the principal veins are generally N. of E. and S. of W., thus 

 having the same direction as the layers of granitic rocks or 

 elvans, and as the strata of the schistose rocks ; and also that 

 these veins are crossed by others nearly at right angles. I be- 

 lieve that I first pointed out the correspondence between the 

 directions of veins, and of joints or seams, which intersect both 

 granite and slate, dividing them into regular concretions ; this 

 suggestion was published in my paper above alluded to, and 

 thus concludes : " this view of the subject explains why the dif- 

 ferent series of veins cross each other, and why the veins of each 

 series are respectively parallel." At the Oxford Meeting of 

 the British Association in 1832, I entered at some length into 

 an explanation of this opinion, a brief notice of which will be 

 found in the first volume of the printed Reports, recommend- 

 ing this as a subject deserving the consideration of geologists ; 

 and this notion is still further developed in the work which 

 I published during the past year. 



This statement shows that observations have been already 

 instituted in Cornwall to compare the direction of the veins 

 not only with the layers of granite, but also with those of the 

 schistose rocks ; and I may add that a considerable mass of in- 

 formation on this subject has been collected by Mr. Henwood. 



I regret that I have been compelled thus publicly to notice 

 a matter in which I am personally interested ; but I could not 

 pass over in silence Prof. Sedgwick's omission to allude to what 

 had already been done on the subject of his suggestion and 

 recommendation, without appearing to sanction an infringe- 

 of the " good principle suum cuique" which ought always to 

 be maintained in scientific intercourse. 



LVII. A concise Method of determining the Function X 2 in 

 the Application of Sturm's Theorem. By J. R. Young, Esq. 

 Professor of Mathematics in Belfast College.* 



I^HE valuable theorem which M. Sturm has discovered for 

 the separation of the roots of numerical equations, was, 

 till very lately, almost entirely unknown to British mathema- 

 ticians. Yet the memoir which embodies this discovery, 

 though not printed till July in the present year, was read be^ 

 fore the Academie des Sciences so long ago as 1829; since 

 which period it has been gradually disseminated throughout 



* Communicated by the Author 



