Mr. J. D. Smith on the supposed new Metal Doniuvi. 255 



Now the objection I urge is this: that although the "ana- 

 lytical artifice" used by Poisson will lead to only one series 

 ot" Laplace's coefficients, it does not at all follow that I cannot 

 discover another analytical artifice which shall lead to another 

 development. For instance, suppose « and /3 are two arbi- 

 trary constants, then I can easily, a jniori, conceive it j)ossible 

 that f[^, vj/, «, |S) can be developed in a series of Laplace's 



coefficients Yq + a.Y■^ + a^Y^^. + ^'y one process, and 



also in another series Zg + /3 Z, + ^'^ 7i^+ by another 



process, and yet that when « = 1 and /3 = 1 the correspond- 

 ing terms of these series shall not be identical. To prove that 

 they are identical is the object of my communication in your 

 June Number; which 1 hope Disjota will again peruse, and 

 I think he must then see that " his observations fall to the 

 ground," since they have been directed to a wrong point. 



In reply to the concluding paragraph of Disjota's commu- 

 nication I refer him to the same volume and page of the Cam- 

 bridge Phil. Trans, as before; and he will learn that the 

 Astronomer Royal was the first to point out that Laplace had 

 assumed, and not proved, thaty(fl, \{/) admits of only one de- 

 velopment of the form required, and that Mr. Ivory had men- 

 tioned this proposition of Laplace's without making any ob- 

 jection to it. I am. Gentlemen, yours, &c. 



Cains College, Aug. 12, 1836. JoHN Henry Pratt. 



LII. Experiments on the supposed new Metal Do?iium. 

 By Mr. J. D. Smith.* 

 tTAVING been led to question the elementary nature of 

 -■--'■ donium, from an experiment on artificial ultramarine 

 hereafter noticed, I resolved on making some further re- 

 searches to satisfy myself as to the existence or non-existence 

 of this substance as a distinct metal. Circumstances oblio-ed 

 me to defer this examination until the present time; but now, 

 from the particulars of the experiments I shall detail, I have 

 no hesitation in expressing my perfect conviction that this 

 supposed new body is a mere mixture of alumina with a mi- 

 nute portion of peroxide of iron. 



Some artificial ultramarine having been digested in dilute 

 hydrochloric acid, and the filtered solution tested with hydro- 

 sulphuric acid, for the purpose of ascertaining whether any 

 metallic substance was contained in it, no precipitate was 

 produced ; but on the addition of a little ammonia a copious 

 green precipitate fell, which exactly coincided with Mr. Ri- 



• Communicated by the Author. A notice of Mr. Richardson's experi- 

 ments on Donium was given in our Number for August, p. 157. 



