FEA 
for 1799 ; and Wollaston for 1800 ; which 
three last are in the journal last quoted. 
The fata morgana seems to depend upon 
the general principles of looming, which 
Wollaston has very successfully displayed, 
together with the reflection from particles 
of water floating in the air. These parti- 
cles doubtless assume prismatic figures 
by coagulation ; and it is, perhaps, a mis- 
take to suppose them to be spherical, even 
at their primary condensation, in the fluid 
state of minute floating particles. 
FATHOM, a long measure containing six 
feet, chiefly used at sea for measuring the 
length of cables and cordage. 
FEATHER, in physiology, a general 
name for the covering of birds; it being 
common to all the animals of this class to 
have their whole body, or at least the 
greatest part of it, covered with feathers or 
plumage. 
There are two sorts of feathers found on 
birds, viz. the strong and hard kind, called 
quills, found in the wings and tail ; and the 
other plumage, or soft feathers, serving for 
the defence and ornament of the whole 
body. All birds, so far as yet known, moult 
the feathers of their whole body yearly. 
The feathers of birds make a considerable 
article of commerce, particularly those of 
the ostrich, heron, swan, peacock, goose, 
and other poultry ; for plumes, ornaments 
of the head, filling of beds, and writing 
pens. There are scarcely any birds but what 
bed-feathers may be procured from, par- 
ticularly those of the domestic kind; yet 
swans, geese, and ducks, are those that fur- 
nish most, and the best. Geese are plucked 
three times a year, towards the end of May, 
about Midsummer, and at the latter end of 
August ; but chiefly when the feathers are 
ripe, that is, when they are perceived to 
fall off of themselves. The feathers of dead 
birds are in the least esteem, upon account 
of the blood imbibed by the quill, which 
putrifying, communicates an offensive smell 
to the feather, and takes some time to 
evaporate ; for which reason live birds 
should not be stripped till their feathers 
are ripe. They are imported in this coun- 
try from Poland and Germany. They are 
divided in white, half grey, and grey, and 
valued accordingly. The best feathers 
should be white, downy, void of large 
stems, fresh, and sweet. Care should be 
taken that no sand be intermixed, which is 
frequently practised to encrease the weight. 
Ostrich feathers are dyed and dressed by 
the feather-dressers, to serve as ornaments. 
FEC 
They are a very costly article, brought to 
us from Africa, and particularly the coast of 
Barbary. See Down. 
FEATHER edged, among carpenters, an 
appellation given to planks or boards, which 
have one side thicker than the other. 
Feather, prince’s, a plant otherwise 
called amaranth. See Amaranthus. 
FECES. The excrementitious matter 
of animals, evacuated per anum, consists of 
all that food which cannot be employed for 
purposes of nutrition, considerably altered, 
at least in part, and mixed or united with 
various bodies employed during digestion 
to separate the useless part of the food 
from the nutritious. An accurate exami- 
nation of these matters has long been wash- 
ed for by physiologists, as likely to throw 
much new light on the process of digestion ; 
but it must be admitted that our knowledge 
on this subject is still very imperfect. Some 
of the older chemists have turned their at- 
tention to the excrements of animals ; (Van 
Helmont’s Custos Emms, sect. 6 ; Opera 
Helmont, p. 247 ; Neumann’s Works, 
p. 585.) but no discovery of importance 
rewarded them for their disagreeable la- 
bour. Vauquelin has ascertained some cu- 
rious facts respecting the excrementitious 
matter of fowls; and in the summer of 
1806, a laborious set of experiments on hu- 
man feces was published by Berzelius, un- 
dertaken, as he informs us, chiefly with a 
view to elucidate the function of digestion. 
(Gehlen’s Jour. VI. 509). About two 
years before, Thaer and Einhof had pub- 
lished a similar set of experiments on the 
excrements of cattle, made chiefly to dis- 
cover, if possible, how they act so power- 
ful as manure. (Ibid III. 276). 
The human feces, according to the expe- 
riments of Berzelius, were found to contain 
Water 
Vegetable and animal remains ... 
.. 7.0 
Bile 
Albumen 
Peculiar extractive matter 
Salts 
Slimy matter, consisting of resin 
of bile, peculiar animal mat- 
>14.0 
ter, and insoluble residue 
> 
100.0 
To Vauquelin we are indebted for an 
analysis of the fixed parts of the excrements 
of fowls, and a comparison of them with the 
fixed parts of the food; from which some 
