PROCEEDINGS OF THE CHEMICAL DEPARTMENT. 393 



14. Instructions for weighing the crop, with schedules for 

 recording the results, shall be sent to each experimenter at a 

 later period. 



When the season for weighing approached, the folio wing- 

 additional instruction for weighing was issued : — 



1. Weigh bulbs and leaves separately, recording the weights 

 of both. 



2. A potatoe weighing machine is that best fitted for the 

 experiment, and it will be found most convenient to take it into 

 the field, and place it close to the plots. 



3. Provide three boxes or large baskets, which can be placed 

 on the weighing machine in which to weigh the crop. It will 

 be advisable to make these all the same weight, by fixing pieces 

 of lead to the lighter ones. 



4. Two men or women put the produce of each plot into the 

 boxes or baskets, and carry it to the machine, beside which the 

 experimenter sits, adjusts the weights, and notes them in his 

 book. 



5. Deduct the weights of the boxes or baskets, and should 

 these not be the same, care must be taken to number them, and 

 note the number of each weighing, so that the proper weight 

 may be deducted in each case. 



At a subsequent period each experimenter was furnished 

 with a set of tables, in which the results could be recorded in a 

 uniform manner. 



We shall consider separately the results of the two different 

 series of experiments which were undertaken. 



1st Series. — Experiments with Soluble Phosphates, from 

 tji pes of the great sources, Minerals, Bone-ash, and Guano, 

 with comparison between Gelatine and Sulphate of 

 Ammonia. 



The experiments of this series were undertaken for the pur- 

 pose of determining, 1, Whether there is any difference in the 

 manurial effect of soluble phosphates, that is, of phosphoric acid 

 in a condition in which it easily dissolves in water according as 

 it is derived from different forms of insoluble phosphate of lime ; 

 and, 2, To ascertain whether there is any difference in the effect 

 produced by ready formed ammonia (in the state of sulphate), 

 and a substance such as gelatine, which does not contain that 

 compound, but only yields it gradually in consequence of the 

 decomposition which it undergoes within the soil. 



In regard to the first of those questions, when looked at from 

 a purely chemical point of view, I have already frequently given 

 it as my opinion that no difference ought to exist. So long as 

 the phosphates are insoluble, it is consistent with all our know- 



2 c 



