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of other quadrupeds, and in greater or less degree according to the 

 different qualities of their food, it was natural to expect some cor- 

 respondent peculiarities in the gizzards of those birds which feed on 

 grass, to fit them for digesting this kind of food. 



With this view the author has examined the gizzards of the goose 

 and swan, in comparison with that of the turkey, which feeds on a 

 different kind of food. 



For the purpose of rendering the fibres distinct, so as easily to be 

 traced, the gizzards of each were boiled, after having been previously 

 filled with plaster of Paris. In the turkey the two muscles, of which 

 the gizzard consists, are of unequal strength, that on the left side 

 being considerably stronger than that on the right. These muscles, 

 by their alternate action, produce a constant friction on the contents ; 

 for though the direct pressure inwards is very great, the lateral mo- 

 tion occasions the force employed upon the substances contained, to 

 be applied in an oblique direction, as Spallanzani and others have 

 observed. 



The internal cavity being of an oval form, like a pullet's egg, 

 rounded on all sides, does not allow the opposite sides ever to come 

 into contact; so that the food is triturated merely by the intermixture 

 of bodies harder than itself. 



In the goose and swan, on the contrary, the cavity is flattened, 

 with its edges very thin. The surfaces applied to each other are, 

 however, not plane surfaces ; but a concave surface is applied to one 

 that is convex ; and in the left side the concavity is above ; but the 

 curvature changes, so that on the right side the concavity is below. 

 In these gizzards the horny covering of their surface is much stronger 

 than in the turkey, and rough ; so that by a sliding motion of the 

 parts opposed, the food is ground, although they do not admit the 

 intervention of hard substances of a large size, and almost without 

 requiring such assistance. 



In the lower part of the oesophagus of these birds, the author ob- 

 serves an enlargement, which he considers peculiar to them, and 

 thinks it answers the purpose of a reservoir, in which the grass is re- 

 tained, macerated, and prepared, as in ruminating animals, for the 

 subsequent process of rumination. 



Observations on Atmospherical Refraction as it affects astronomical 

 Observations ; in a Letter from S. Groombridge, Esq. to the Rev. 

 Nevil Maskelyne, D.D. F.R.S. Astronomer Royal. Communicated 

 by the Astronomer Royal. Read March 28, 1810. [Phil. Trans. 

 1810, p. 190.] 



Mr. Groombridge being in possession of a transit circle four feet 

 in diameter, made by Troughton, undertook a series of observations 

 upon circumpolar stars, for the purpose of determining the latitude 

 of his observatory. 



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