POUCHET, ON ATMOSPHERIC MICROGRAPHY. 133 



It is remarked also, that in proportion to the elevation 

 reached on mountains or on buildings, the amount of fecula 

 mixed with the atmospheric detritus is diminished. In the 

 Abbey of Fecamp, which is below the level of the ground, 

 and situated in the middle of the town, starch abounds in 

 the dust of its chapels. In the Cathedral of Rouen a con- 

 siderable quantity is met with in the lower part of the 

 tower of Georges d'Amboise, the proportion gradually dimi- 

 nishing as we ascend. Whilst still abundant in the ancient 

 dust found in the roof of the choir, it becomes more and 

 more rare when we mount into the spire. Very little is 

 found at the base of the cast-iron pyramid, and not a single 

 grain at its summit. 



In an isolated chapel situated on the sea-shore, and built 

 on a beach about 110 metres in elevation, the dust lodged 

 on a statue was composed, in great part, of calcareous 

 particles, derived from the sides of the mountain, and con- 

 veyed by the wind to the floor of the building, which is open 

 day and night to pilgrims. In the same situation were also 

 found a great number of scales of lepidopterous insects, which 

 had, doubtless, often sought shelter there ; but very rarely was 

 a grain of starch perceived in the field of the microscope ; 

 whilst in the detritus of towns, on every trial, several grains 

 of a medium size, and a considerable number of more minute 

 dimensions, would have been noticed. 



A battery also placed on the shore, and in an isolated situa- 

 tion, and which had not been opened for sixty years, afforded 

 a black dust, which was as poor in starch as that of the 

 chapel above mentioned. But the dust itself was of a wholly 

 different nature, being composed almost entirely of very 

 angular, transparent, colourless particles of silex. The 

 starch was so scarce in this dust, that often not more than 

 a single grain could be discovered in a dozen observations. 



This dissemination is a phenomenon so general and so 

 widely diffused in places where wheat is used for food, that 

 there is no nook or corner into which starch does not in- 

 sinuate itself with the air. It is found in everything, and in 

 all situations into which the latter penetrates. The most 

 obscure corners of our Gothic buildings have afforded this 

 substance in the ancient dust which had never been dis- 

 turbed in the memory of man. I have even found it in the 

 interior of the cavity of the tympanum in the skull of a 

 mummified dog which I procured from a subterranean 

 temple in Upper Egypt. M. Ch. Robin, whose observations 

 accord with mine, has discovered starch on the surface of 

 the human skin, whence it may be procured by scraping 



