During the present summer a stable in Philadelphia burned down, undoubtedly from heat generated by manure piled against it. Those interested in gardening do not understand, as clearly as they should do, what is meant by spontaneous combustion. The following remarks on the burning of the great tanneries at Chattanooga, offered by the Drugman, of that place, will be profitable to our readers:

"Of late the news from fires seems to be replete with ' spontaneous combustion' as the cause; especially is this true of the accounts of the fires of factories and large mills. We are inclined to the opinion that we saddle on combustion a much greater load than necessary. We are informed that a recent large fire and total destruction of one of the largest tanneries in the world, in fact perhaps the 'largest, that the origin of the fire is unknown, but supposed to be spontaneous combustion.

"It is a notorious fact in chemistry that refuse woody matter, such as sawdust, spent tanbark, rags, will generate a great amount of heat in their processes of fermentation or decomposition, to proceed with a distinction without a difference, and if any of the essential or fixed oils possessing a low combustion are brought in contact with and remain so for any length of time, there is not the least doubt but flames might ensue.

"This process of spontaneous combustion, the so much talked of laws governing it, are very little understood. All know to have fire we must have oxygen. Now, the oil has an affinity for oxygen, and the spongy nature of spent bark, sawdust, rags, and the like, affords an immense amount of surface for the contact with the air and with no avenue for the escape of generated gases; hence this chemical combination follows, and the operation is sufficiently rapid to generate heat enough to ignite the mass. Even whale oil has been known to take fire spontaneously when subjected to these influences and under these circumstances, and varnish, linseed oil, turpentine, as well as many other hydro-carbons used in the arts and manufactures, are almost sure to create trouble, resulting in disaster, when similarly treated.

"We have no means of knowing the origin of the fire in question; nevertheless there can be no doubt that many a destructive fire has an ultimate origin in the oil-soaked waste used in cleaning machinery and thrown carelessly among substances as indicated above. A little wise precaution will avert the penalty for a like ignorance or carelessness has been paid over and over again by oil, varnish, and seed users".

The time will soon come when we shall have reports of burning greenhouses, and wonders expressed why they burned. This paragraph will therefore be timely.