CHEMICAL SCIENCE. 267 



Having ascertained that arsenic could be absorbed by plants without 

 destroying their vitality, Professor Davy next proceeded to experiment on 

 the super-phosphate, by planting a small cabbage-plant in a pot containing 

 one part of the manure to three of mould. At the end of three weeks the 

 top was cut off, and appeared green and healthy; and on testing one hun- 

 dred and thirteen grains of the cabbage, very distinct indications of the 

 poison were observed. But, as the amount of super-phosphate used in this 

 experiment was much more than would have been used in ordinary cases, 

 Professor Davy procured some turnips to which six cwt. of the manure had 

 been used per Irish acre, and from two Ibs. weight of the roots which had 

 been carefully washed and boiled for three hours in thirty-six ounces of 

 distilled water and three ounces of hydrochloric acid, striking evidence 

 was afforded of the presence of arsenic in the turnips. On testing the 

 brown acid used by the manure-makers, as much as one grain of white 

 arsenic was discovered per ounce of vitriol. It is necessary to state, that the 

 utmost caution had been taken to ascertain that no arsenic existed in any of 

 the reagents employed in the experiments. These facts show the extreme 

 caution which is necessary in the formation of conclusions based on the 

 presence of a minute quantity of arsenic in the body of a person suspected 

 to have died from poisoning, as the small amount discovered in the liver, or 

 stomach and viscera, might have been received into the system with the veg- 

 etable or even aiiimal food taken by the individual. 



ATMOSPHERIC DUST. 



This subject has been recently brought before the French Academy by M. 

 Pouchet, in a paper entitled " Etude des corpuscles en suspension dans 1'at- 

 mosphere." The atmosphere which surrounds us holds in suspension a 

 mass of corpuscles, the detritus of the mineral crust of our globe, animal 

 and vegetable particles, and the debris of all that is used for man's purposes. 

 These diverse corpuscles are proportionably more numerous and voluminous 

 as the atmosphere is more or less agitated by the wind, and it is to these that 

 the term dust has been applied. 



The author enumerates the various corpuscles of mineral, animal, and 

 vegetable origin with which the air is loaded. Under the latter the vege- 

 table products he mentions especially particles of wheat, which are 

 always found mixed with dust, be it recent or old, as well as those of bar- 

 ley, rye, potatoes, which have been discovered in rare instances. " Aston- 

 ished at the proportional abundance of flour which I have found among the 

 atmospheric corpuscles," says M. Pouchet, " I undertook the task to examine 

 the dust of all centuries and of all localities. I have explored the monuments 

 of our large cities ; those of the shore and those of the desert ; and in the 

 midst of the immense variety of corpuscles that universally float in the air, 

 almost always have I found the dust of grain, in greater or lesser abundance. 

 Endowed with an extraordinary power of preservation, years seem scarcely 

 to have altered it. 



" Whatever may be the antiquity of atmospheric corpuscles, we find 

 among them the dust of grain yet recognizable. I have discovered it in the 

 most inaccessible retreats of our old Gothic churches, mixed with their black- 

 ened dust of eight centuries; I have met it in the palaces and hypogees of 

 Thebes, where it dates back perhaps to the epoch of the Pharaohs. I have 

 found it even in the interior of the tympanal cavity of the head of a mumini- 



