594 Addition to Mr. Hannam^s Paper on Sulphuric Acid. 
to arrive at a conclusion that he dare confide in. This need not 
be a subject of wonder. He has always been led by surface-ap- 
pearances, and the same surface-appearances that are favourable 
indications in one district may be, and are, unfavourable in 
another. 
Farmers in general have hitherto been in the habit of judging 
of the fertility or barrenness from colour, consistence, and surface- 
appearances, the two former sharing more or less in the business, 
according to the extent of information on the subject possessed by 
the party. These things, it must always be understood, will 
materially assist us ; but I think enough has been shown to de- 
monstrate that, if relied upon alone, they are inadequate to the 
purposes for which they have hitherto been in use. 
February, 1844. 
XXXI II. — Addition to Mr. Hannams Paper on Sulp>huric Acid. 
SiNCK the foregoing article was written, my attention has been 
called to the experience of Mr. Tennant of Shields, near Ayr. 
The particulars of these experiments have, through the kindness 
of Mr. Campbell of Craigie, been forwarded to me, and I cannot, 
on account of the intrinsic value of the information which they 
afford us, omit to call special attention to them. Mr. Tennant's 
trials extend over several years, and during the present season 
have been on a scale of magnitude much greater than any which 
have yet been recorded — a better proof than any other that can 
be given of the satisfactory results of the earlier trials. 
The following are the particulars politely furnished by Mr. 
Tennant himself: — 
" After reading Llebig's work on agricultural chemistry, about 
four years ago, I resolved to try the experiment of using dissolved 
bones, and procured 2G bushels of bones, and 2 bottles of sulphu- 
ric acid, at \d. per lb. ; about 190 lbs. each. This mixture I 
applied to 9 acres of land, with 20 carts of dung per Scotch acre, 
and was highly satisfied with the result. Some drills on which I 
omitted the solution aj)peared one-third deficient; and one drill 
to which I gave a douhle quantity appeared to have nearly double 
the iceiyld of crop to the row next it, which had no solution. The 
whole 9 acres were equal to the remainder of the field, which had 
farm-manure, and \^ cwt. of Peruvian guano, at 2Gs. per cwt. 
"The amount of dressing applied in the above trial was, there- 
fore, about 3 bushels of bones and lbs. of acid per acre, cost- 
ing about lis. per acre. 
" Next year (1843) I dissolved 200 bushels, and gave 5 bushels 
