424 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



perfectly normal, the removal of the hay was commenced on 

 the 19th. The upper portions were so sweated that drops 

 of moisture accumulated on the hay. At the depth of three 

 feet, in another place at o;ily one and a half feet, the hay be- 

 came dry and hot, and a distinct empyreumatic odor was 

 recognizable. At five feet sparks appeared in the stack, and 

 at the same time also, suddenly, among the hay that had 

 been thrown onto the wagon ; and afterward it occasionally 

 burst into flame on the wagon, although water had beeh ap- 

 plied in the stack. In cutting out a space to separate it 

 from the smaller stack, which was unaffected, such quantities 

 of an irrespirable gas were given out, probably carbonic ox- 

 ide, that the workmen were driven back in from one to two 

 minutes. The burning portion seemed to form a central nu- 

 cleus to within one and a half feet of the bottom. It was in 

 the condition of true carbon, with complete retention of the 

 structure of the grass, and the property of leaving a mark on 

 paper. It seems, therefore, that hay, as previously suggested 

 by Buchner, in decomposing in this way, is converted into a 

 highly porous carbon, contaminated with matter suitable for 

 rapid oxidation, and, like many other forms of carbon, possess- 

 ing pyrophoric properties, not, however, when cold. The 

 presence of a considerable amount of empyreumatic matter 

 and some water was demonstrated by heating it in a flask. 

 After expulsion of these by continued heating, it cooled rap- 

 idly in the open air w^ithout igniting. Upon heating to 

 482-570, in a flask, in an oil-bath (to avoid possibility of 

 direct ignition, as well as to secure complete expulsion of the 

 empyreumatic matter), and then pouring it on a table, in a 

 little pile, it rapidly fell to a temperature which could be 

 borne by the fingers ; but in a few minutes increase of tem- 

 perature became perceptible, until suddenly portions began 

 to glow, showing that the presence of empyreumatic matter 

 and an elevated temperature are conditions of its pyrophoric 

 property. By heating a portion in a small beaker in an oil- 

 bath, and throwing it in a little pile upon a table, when it 

 ignited in several minutes, the temperature at which the 

 normal hay passed into this carbonized condition was found 

 to be between the fusing-point of tin and lead (446 to 61 V), 

 an experiment adapted to lecture illustration. 



The fact of spontaneous combustion thus established, it 



