302 Prof. Young's Analytical Investigation of 



Thirty grains of crystals of strontia dissolved in hot water, 

 and precipitated by bicarbonate of potash, gave 16*5 of car- 

 bonate of strontia = 11 '56 strontia; a second thirty grains gave 

 precisely the same result : so 



Stron. Stron. Water. 



30 11*56 + 18*44, or, 51*8, one equivalent 



of strontia combined with 82*62, rather more than 9 equiva- 

 lents of water. 



Although these experiments do not agree with those either 

 of Mr. Phillips or Mr. Smith, their coincidence with each other 

 appears to show that these two metallic oxides do not behave 

 precisely the same with respect to water. 



I am, Gentlemen, yours, &c, 

 Shawford near Bath, Aug. 18, 1837. Henry M. Noad. 



XXXVI. Analytical Investigation of Professor Wallace's Pro- 

 perty of the Parabola. By J. R. Young, Esq., Professor of 

 Mathematics in Belfast College.* 



IN the Philosophical Magazine for August 1836, a remark- 

 *- able property of the parabola, first established by Professor 

 Wallace, is made the subject of a communication from Mr. 

 Lubbock; in which communication that distinguished mathe- 

 matician has given a proof of the theorem upon the principles 

 of analytical geometry. 



In a subsequent Number of the Magazine, that for January 

 1837, two other analytical investigations were given; one by 

 Mr. Greatheed of Trinity, and the other by Mr. Holditch of 

 Caius College, Cambridge; and a neat geometrical proof was 

 at the same time offered, differing but little from that of Pro- 

 fessor Wallace himself. 



Ingenious and interesting as these several investigations are, 

 they can, I think, scarcely be regarded as more than mere 

 verifications, by analysis, of a previously known geometrical 

 truth ; in as much as they do not exhibit the steps by which 

 an analyst would be likely to be led to such a property, unless 

 it were anticipitated at the outset. It is certain also that no 

 analytical investigation hitherto given is comparable, on the 

 score of simplicity, with the geometrical proof; although it 

 would be premature to assert that analysis is incompetent to 

 furnish a proof equally simple and elegant. 



The investigation which I here offer is remarkably easy ; it 

 differs essentially from those hitherto given, and will I think 

 bear a favourable comparison with the geometrical method. 

 « Communicated by the Author. 



