330 Chemical Changes in the Fermentation of Dung. 
what I conceive to be the proper mode of fermenting ma- 
nure. 
I. A heap of sods and weeds containing about 40 cartloads 
was put to rot, and allowed to remain two or three months. 
There being a large proportion of earth in the heap, it was em- 
ployed to mix up with the contents of two very large cesspools 
which received the drainage of eight 10-roomed houses, and had 
not been emptied for 17 years. The odour given off by the 
accumulation was most sickening, and large bubbles of gas 
generated by the decomposing mass were constantly breaking 
upon the surface of the water. The solid residue was mixed 
with nearly its own bulk of the soil and sods, and was thus ren- 
dered so free from smell as to be carted past a terrace of houses 
in the daytime without a complaint. About 35 loads of refuse 
was removed. With this heap was mixed in a few weeks its 
own bulk of horse, cow, and pig dung which soon formed a 
black homogeneous mass almost odourless. It gave off no per- 
ceptible gas, and proved in the end as powerful a manure as 
could safely be applied to land. Some York regent potatoes 
planted with it grew tops nearly 6 feet long with a corrQsponding 
crop of tubers, and Early shaws at 2 ft. 6 in. from row to row 
could not be dug the second week in July without first removing 
the tops. The men who dug this crop stated that it was the 
best they ever dug at the time of year. 
II. Four cwt. of pigeon dung was mixed with twice its weight 
of soil and kept for about five months exposed to weather. It 
was once turned. No smell of ammonia was perceived during 
that period, nor would test-paper indicate escape of ammonia 
save when the heap was tui'ned. A very slight odour was then 
perceptible, and by careful management a feeble reaction could 
be detected by the test-paper. I believe the influence of this 
was superior to 4 cwt. of the best guano applied in the usual way. 
III. A person in the neighbourhood had accumulated the 
blood from the public slaughter-houses for many weeks. At the 
time of which I speak the mass consisted of more than a dozen 
tons of black coagulum which was putrefying in a hole. The 
stench given off could be smelt for lialf a mile in the direction of 
the wind, and every one was loud in denouncing the effluvia. 
The most sceptical would have admitted the formation and 
escape of phosphuretted hydrogen had he been kept a few 
minutes on the lee side of the mass. I purchased this and had 
it carted within a hundred yards of a number of good houses. 
It was placed to the S.W. so that the offensive stench miglit be 
borne on the wind to the inhabitants, and was left a day un- 
covered. Complaints were numerous, threats of legal pro- 
ceedings were made, and when sufficient attention was thus 
