species of the Genus Larus, or Gull Tribe. 1 
The general appearance of this bird is neat and elegant, and 
the gait is graceful and dignified. Its note very nearly resem- 
bles that of the Larus rissa or kittiwake, but is rather more 
plaintive. With respect to what has been said regarding the 
circumstance of this bird pursuing the common gull, and obli- 
ging it to disgorge part of its food, it appears more probable 
than the opinion which supposes that the latter is hunted 
down by it for its excrement. All the gull tribe possess the 
faculty of vomiting easily what the}? have swallowed ; but to 
suppose that they have a voluntary power over digestion, would 
be to admit a violation of the natural habits of all animals. 
Art. XXVII. — On the Specific Gravity of Barley and Scotch 
Bigg , with the description of a New Instrument for Mea- 
suring it. In a Letter from the Reverend George Skene 
Keith, D. D. to Dr Brewster. 
Sir, 
I beg leave to communicate for your valuable Journal an ac- 
count of the comparative specific gravities of barley and Scotch 
bigg, of various weights per bushel, and of a new instrument 
which was made under my directions, for ascertaining the spe- 
cific gravity of different kinds of corn. 
I have been induced to inquire into the relative values of bar- 
ley and Scotch bigg, in consequence of the acts of 1802 and 
1819, which imposed equal duties on malt made from these two 
kinds of grain, which are so very unequal in point of weight per 
bushel, of marketable price, of extract or saccharine matter by 
the brewer, and of ardent spirits by the distiller ; — in regard to 
all which subjects I had made experiments, and instituted cal- 
culations previous to 1804. But in the Report of the experi- 
ments by Drs Hope, Coventry and Thomson, printed by order 
of the House of Commons in June 1806, I found, in the Table 
of Raw Grain, among other anomalies, that Suffolk barley, of’ 
the second quality, had a specific gravity of 1.307, while its 
weight per bushel was only 49-250 lb. ; while Berwickshire bar- 
ley of the first quality, and weighing 52.062 per bushel, had 
