410 JWiscellanies. 



8. Prof. Joslin, of Union College, has published an ingenious 

 memoir on vision, presenting some novel facts and opinions, which 

 cannot fail to be interesting both to the anatomist and optician. — See 

 Phil. Jour, of the Med. Sciences for May 1831. 



9. Prohlem* — To assign rational numbers for the length of the 

 sides of a right-angled triangle. Assume m, n, p, any rational num- 

 bers, so that w>p. Then m{n^-{-j)^), m{n" —p^) and 2mnp v^rill 

 he the sides of the required triangle. 



Demonstration: (m^{n^ —p''y-\-(2mnpyy=m{n^-{-p^). 

 Example: Put m=l, p = l, n=2 ; then by the foregoing formula 

 we have the sides of a well known right-angled triangle, viz. 3, 4 and 5. 



10. Topaz in the White Mountains of JYeiv Hampshire. 

 Extract of a letter from Prof. Hitchcock to the Editor, dated June 9, 1831. 



Mr. Oakes, of Ipswich, showed me, the other day, an interesting 

 specimen from the White Hills. He labeled it, " from the falls of 

 Amonoosuck, one mile and a half, down the river, from E. A. Craw- 

 ford's — White Mountains — close to the road — a single loose speci- 

 men." It is a coarse granite, whose felspar is flesh colored and the 

 quartz smoky ; both being distinctly crystalized. Mixed with these, 

 are several prismatic terminated crystals, which I have little hesita- 

 tion in saying are topaz ! For they have the hardness of that min- 

 eral, and exhibit a lamellar structure at right angles to the axis of the 

 prism — a character, which I have found very decisive of this mineral 

 when crystalized. These crystals are limpid, and resemble very 

 ranch the topaz from Brazil. 



11. Marl for manure. — We have received a specimen of calca- 

 reous materials mixed with earthy matters from Mr. Burner Oakes 

 of Baltimore. It appears, from trial by acids, to contain from one 

 half to two thirds of calcareous matter, evidently the ruins of disin- 

 tegrated and decomposed shells, among which, pectens are numer- 

 ous, and is obviously a portion of a great oceanic deposit, similar to 

 those found so extensively from New Jersey to Florida and Louisiana. 



* Remark. — The author (Mr. Gould.) became acquainted with Mr. Wheeler's 

 problem, in consequence of reading the proof, and therefore hi.s problem is allowed 

 to appear in the present No. Since the above was in type, he suggests, that he 

 has found the same solution in Bonnycastle's Algebra. 



