142 On the Preservation of Provisions and Goods. 



a week : no hydrogen was evolved. A small phial was nearly 

 filled with iron-filings, some boiled water was pomed in so as to 

 form a thin layer over them; oil was placed on the water, a bent 

 tube was fitted to the phial, and the end was left under a receiver 

 during a week, as in the former experiment. No trace of hydro- 

 gen was discovered. A test tube was nearly filled with mercury, 

 some paper containing iron-filings, moistened with warm water, 

 was forced in a short way; the tube was then filled to the brim 

 with mercury and was inverted over the same fluid. It was kept 

 inverted during five days ; no hydrogen was given ofi^. Some 

 paper, containing moistened iron-filings, was forced up to the 

 end of a test-tube with a quill ; the tube was then kept inverted 

 over mercury. The mercury rose rapidly in the tube until it at- 

 tained a certain height, where it remained stationary, evidently 

 from the absorption of the oxygen of the atmospheric air con- 

 tained in the tube, as was to be expected from the experiments 

 of Dr. Marshall Hall. The glass-vessels containing the water 

 and iron were moved several times during the course of thesR 

 experiments : perhaps a state of perfect rest may be necessary for 

 the decomposition of water by a large quantity of iron at ordinary 

 temperatures. But it appears difficult to me' to reconcile these 

 experiments with the accoimt which states that It takes place 

 rapidly. 



In a former paper I stated that I had put some fresh meat 

 in water covered with oil, with some iron to abstract oxygen ; and 

 that its appearance was unchanged at the end of seven weeks. 

 In the first place I neglected to state that the meat had been 

 boiled; in the second place I judged of its state of preservation 

 entirely from its appearance through the glass-vessel. After al- 

 lowing it to remain ten weeks in the water, I removed it : it was 

 found softened, the structure was not much changed, but its odour 

 was offensive. To keep meat as dry and as cool as possible du- 

 ring warm weather is the plan that ought to be attended to. 



Where bales of goods are moist by any accident, and it is not 

 in the power of persons to unpack them immediately to dry the 

 goods ; it may perhaps be found useful, for preventing mildew, 

 to immerse them in water, and to cover its surface with oil. 



I have found that the decay of vegetable substances is very 

 much retarded by immersing them in water covered with oil and 

 deprived of oxygen by iron. A vegetable substance may be sunk 

 by attaching a weight to it; any iron employed for abstracting 

 oxygen ought to be previously removed. 



Water in a situation where it is scarce may be preserved, I 

 presume, in an open cask by covering its surface with a thick 

 layer of oil, and by putting in recently prepared charcoal. The 

 trouble of preparing powdered charcoal is an objection to its use. 



Large 



