666 



STATE BOARD OF AGRICULTURE. 



about one day old when they were added to tlie soil. For convenience 

 and comparison only the pure solid was used. They were employed in 

 the proportion of 0.0, 5, 10, 20, and 40 t(ms per acre, and 100% of cow 

 and horse. Their moisture content was determined and shown in the 

 table below. It will be seen that their water content is different. No 

 correction was made for these differences in the weight of the manure 

 added to the soil, consequently the actual amount of dry matter was 

 not the same. Since the moisture consists of urine and this undergoes 

 fermentation, it also adds heat to the soil. 



The preparation of the experiment including, the weight of the soil, 

 name and amount of manure added, the moisture content, etc., are all 

 shown together in the following table: 



TABLE 90.-SHOWING PLAN OF EXPERIMENT. 



Weight of soil. 



Tons 

 manure 

 per acre. 



396 lbs 



396 lbs 



396 lbs 



396 lbs 



396 lbs 



396 lbs 



6 Kilos horse manure, 

 6 Kilos cow mannre. 



0.0 

 5.0 

 10.0 

 20.0 

 30.0 

 40.0 



Per cent 



moisture 



C. M. Expt. 



17.52 

 17.52 

 17.52 

 17.52 

 17.52 

 17.52 



Per cent 



moisture 



S. M. Ezpt. 



17.42 

 17.42 

 17.42 

 17.42 

 17.42 

 17.42 



"V\Tien the preparation of the experiment was complete the pots were 

 placed in rows on a stand one foot from the ground and kept in a room 

 whose temperature varied very little from day to day. The room was 

 intended for refrigerating purposes and was ideal for keeping the tem- 

 perature constant. 



In the first three experiments the temperature readings were taken 

 by means of mercury thermometers graduated to 1° Centigrade. The 

 results obtained by them were not altogether satisfactory because they 

 did not read closely enough. To obtain mercury thermometers of high 

 precision and the large number required in the present extensive work, 

 it would have entailed considerable expense. To overcome this diflS- 

 culty, it was decided to use thenuocouplos in the present or fourth ex- 

 periment. The principle of such instruments is based upon the fact 

 that when two wires of dissimilar metals are connected end to end and 

 one junction is kept at a constant and the other at a variable tempera- 

 ture, an electrical current is ]>roduccd the amount of which is propor- 

 tional to the difference in temperature between the two junctions. This 

 electrical current is measured by the deflection produced on the galvano- 

 meter. The amount of electrical current is also influenced by the compo- 

 sition of the wires. The combination of certain kinds of elements pro- 

 duces a greater current than others. 



The thermocouples used in the present work were made in this labora- 

 tory especially for the purpose. Their material consisted of No. 18 

 "advance" wire and No. 18 copper wire. They were constructed by 



