Miscellanies. > 
: ‘J Prof. Joslin, of Union College, has published an ingenious 
* rk creed on vision, presenting some novel facts and opinions, which 
"cannot, fail to be interesting both to the anatomist and optician.—See 
~ Jour. 0 © p Medi Singes for May 1831. 
9. Problem.* *_To assign rational mele forthe longi of the 
ee sided a right-angled triangle. Assume m, n, p, any rational num- 
bers, sc . that _n>p. Then m(n?-+-p2), "ie —p*) and 2mnp will 
1e si es sof the required wisiige- 
: : (m? (n? —p?)?+ + (2mip)?)t=m(nt +p"): ye 
' - Ecamp p=1, n=2; then by the foregoing formula 
we have me e sides tof ‘wellknown right-cneled sae viz. 3, 4 ee “s 
10. Topaz in the White ‘Mountains of ™ ew Hampshire. 
Extract of a letter from Prof. Hitchcock to the Editor, dated June 9, 1831. 
Mr. ee of lospich showed, me, the other day, an interesting 
nen fir hite Hills. He la eled pit “ from the falls of | 
3 nA AC gle Ic Ds 
, . erase es: is flesh color 
Gat sou oa being distinctly crystalized. “Mixed with these, 
_ are several prismatic terminated crystals, which Thavé little hesita- 
tion in saying are topaz! For they have the hardness-of that min- 
San, 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 
much the topaz from Brazil. 
11. Marl for manure.—We lave received a specimen of calca- 
reous materials mixed with earthy matters from Mr. Durner 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 i is obviously a portion of a great oceanic deposit, similar to 
id so extensively from New Jersey to Florida and Louisiana. 
z a 43 
“* Remark.—The> author (N os) became acquainted with Mr. wheelers 
_Teading the proof, — therefore his problem is allowed 
eee in type, he suggests, that he 
