PROCEEDINGS OF THE CHEMICAL DEPARTMENT. 215 



practical experience of small experiments, leaned to the opposite 

 opinion. As far as I am myself concerned, I have repeatedly- 

 expressed my conviction, that experiments made on a small 

 scale, with proper care and precautions, ought to give as good 

 results as those in which very large plots are employed ; but I 

 have always recognised the necessity for putting this opinion to 

 the test by a set of comparative experiments, and in the original 

 scheme drawn up for the Committee such an inquiry w r as sug- 

 gested. The propriety of engaging in such a set of experiments 

 was again mooted, but practical difficulties existed in carrying 

 out the proposition at the time, and after mature consideration, 

 the Committee resolved that the small experiments should be 

 continued for another year, leaving the arrangement of set of 

 large and small scale experiments for next season. It was sug- 

 gested, indeed, by one gentleman, that the latter should in all 

 cases precede the former, as they might often form useful guides 

 to show what should be undertaken on the large scale. 



The second matter the Committee had to consider arose out 

 of the particular object of the experiments of 1866. It was urged 

 that, from the very nature of the questions which they proposed 

 to examine, substances not usually employed as manures had 

 been used, and that their interest to the farmer would be largely 

 increased, if, in addition to or instead of these substances, some 

 of the ordinary manures in daily use, such as Peruvian guano, 

 were introduced into the scheme of experiments as points of 

 comparison. The Committee at once recognised the importance 

 of this proposal, and resolved that it should be adopted as far as 

 possible. At the time at which it was made, however, the 

 arrangements were so far advanced, that this could not be done 

 throughout all the experiments, but they were divided into two 

 series, into the second of which Peruvian and Bolivian guanos 

 were introduced as representatives of the two great classes of 

 ammoniacal and phosphatic guanos. 



Plan of the Experiments of 1867. 



The general object of these experiments was to follow out the 

 line of inquiry of the preceding year, with such modifications as 

 experience dictated, and, as just mentioned, with the addition in 

 certain cases of Peruvian and Bolivian guanos. These objects 

 were, — 1st, To compare the effects of ready formed, and what 

 may, for convenience' sake, be called potential ammonia — the 

 former in the state of sulphate of ammonia, the latter in that of 

 glue, the state in which it exists in the bones ; 2d, To compare 

 the results obtained from soluble phosphoric acid, in the form of 

 dissolved phosphatic guano and coprolites, these two substances 

 being taken as the best representatives of what we may call 

 animal and mineral phosphates ; 3d, To ascertain the effect of 



