Account of a numerical Table of elective AiLractions. 53 



The Map that I am preparing, which traces every stream 

 and vale up to its very origin, and shows its connection with 

 the hard and soft, and porous and water-tight strata, and 

 with the principal faults and tilts of the same, in its vici- 

 nity, will, as I trust, somewhat elucidate this difficult sub- 

 ject: oa which I much wish to hear the observations of 

 others of your able correspondents, and am, 



Sir, your obedient humble servant. 



Ram's Head Inn, Disley, Cheshire, JoHN FaREY. 



July 15, 1809. 



*,* In our last vol. p. 263, line 1, the hases to should have been the lasseis 

 q/" three or four different strata &c. Basset, crop, &c., are mining terms for 

 the out-burst or appearance of a stratum on the surface. 



IX. ^fu4 numerical Table of elective Attractions ; uith Re- 

 marks on the Sequences of double Decompositions, By 

 Thomas Young, M.D. For. Sec. R.S.* 



Attempts have been made, by several chemists, to obtain 

 a series of numbers, capable of representing the mutual at- 

 tractive forces of the component parts of diflcrent salts ; but 

 these attempts have hitherto been confined within narrow 

 limits, and have indeed been so hastily abandoned, that some 

 very important consequences, which necessarily follow from 

 the general principleof a numerical representation, appear to 

 Ijave been entirely overlooked. It is not impossible, that there 

 may be some cases, in which the presence of a fourth sub- 

 stance, besides the two ingredients of the salt, and the me- 

 dium in which they are dissolved, may influence the precise 

 force of their mutual attraction, either by affecting the solu- 

 bility of the salt, or by some other unknown means, so that 

 the number, naturally appropriate to the combination, may 

 no longer correspond to its affections ; but there is reason to 

 think that such cases arc rare ; and when they occur, they 

 may easily be noticed as exceptions to the general rules. It 

 appears, therefore, that nearly all the phcenomcna of the 

 mutual actions of a hundred different salts may be correctly 

 represented by a hundred numbers, while, in the usual 



• From PhiloK'phical Transactions for 180!), Pan I. 



D 3 inainur 



