552 
RAY 
RAY 
R A T 
B, being proposed, their relation one to an- 
other may be considered under one of these 
two heads: 1. How much A exceeds B, or 
B exceeds A; and this is found by taking A 
from B or Bfroni A, and is called arithmetical 
reason, or ratio. 2. Or how many times, 
and parts of a time, A contains B, or B con- 
tains A; and this is called geometric reason or 
ratio; (or, as Euclid defines it, it is the mu- 
tual habitude, of respect, of two magnitudes 
pt the same kind, according to quantity; that 
is, as to how often the one contains, or is 
contained in, the other ;) and is found by di- 
viding A by B, or B by A; and here note, 
that that quantity which is referred to another 
quantity, is called the antecedent of the ra- 
tio; and that to which the other is referred, 
is called the consequent of the ratio; as, in 
the ratio of A to B, A is the antecedent, and 
lithe consequent. Therefore' any quantity, 
as antecedent, divided by any quanitv as a 
consequent, gives the ratio' of that antecedent 
to the consequent. 
Thus the ratio of A to B is — , but the ratio 
B 
of B to A is — ; and, in numbers, the ratio 
A 
c , _ ^ . 12 
of 12 to 4 is — — 3, or triple; but the ratio 
4 1 
of 4 to 12 is --- = — , or subtriple. 
The quantities thus compared must be of 
the same kind; that is, such which, by mul- 
tiplication, may be made to exceed one the 
other; or as these quantities are said to have a 
ratio between them, which, being multiplied, 
may be made to exceed one another. Thus 
a line, how short soever, may be multiplied, 
that is, produced so long as, to exceed in 
length any given right line, and consequently 
these may be compared together, and the 
ratio expressed; but as a line can never, by 
any multiplication whatever, be made to have 
breadth, that is, to be made equal to a super- 
ficies, how small soever ; these can therefore 
never be compared together, and conse- 
quently have no ratio or respect one to an- 
other, according to quantity: that is, as to 
how often the one contains, or is contained in, 
the other. See Proportion. 
RATION, a certain allowance which is 
given in bread, &c. or forage, when troops 
are on service, for an officer or soldier. 
Complete rot ion of the small .species. 
Flour, or bread - 14 lbs. 
Beef - - i 
or pork - 4 
Peas - - - - i pint 
Butter, or cheese - i oz. 
Rice - - - - l oz. 
When the small species are not issued, 14 
lbs. of Hour or bread, with 14 lbs. of beef, or 
10 oz. of pork, forms a complete ration ; or 
.3 lbs. of beet, or 2 lbs. of cheese, or hah' a 
pound of rice, forms a complete ration. 
The deductions to be taken for provisions 
from the pay of officers, non-commissioned 
officers, or men, are the same for ail ranks, 
and in all corps, uiid -v the like circumstances 
of service, when serving out of Great Britain, 
on stations where provisions are supplied bv 
tiie public; also, when embarked in trans- 
ports or other vessels, (except when serving 
as marines ;) also when prisoners of war. nr- 
maintained at the expence of Great Britain ; 
also when in general hospitals, whether at 
home or abroad, a deduction of sixpence per 
dav. 
A deduction of threepence halfpenny from 
the pay of every non-commissioned officer 
and private in Jamaica, in New South Wales, 
or Gibraltar. Non-commissioned officers 
and soldiers serving as marines shall not be 
liable to any deduction from their full pay on 
account of provisions. 
Ration for a horse on home service in 17ff6, 
l41bs. of hay, 10 lbs. of oats, 4 lbs. of straw, 
for which a stoppage is made of sixpence. 
The French use the same term, viz. ration 
(is foi-n, a ration of hay ; double radon, 
double ration; de mi-ration, a half-ration. 
RATIONAL is applied to integral, frac- 
tional, and mixt numbers; thus we say, ra- 
tional fraction, rational integer, and rational 
mixt number. 
Rational is applied to the true horizon, in 
opposition to the sensible or apparent one. 
RATIONALE, a solution, or account of 
the principles of some opinion, action, hypo- 
thesis, phtenomenon, or the like. 
RATLINES, or, as the seamen call them, 
Ratlins, those lines which make the ladder- 
steps to get up the shrouds and futtocks, 
hence called the ratlins of the shrouds. 
RATTLE-SNAKE. See Crotalus. 
RAVELIN, in fortification, was antientlv 
a flat bastion, placed in the middle of a cur- 
tin ; but now a detached work composed only 
ot two faces, which make a saliant angle, 
without any flanks, and raised before the cur- 
tin on the counterscarp of the place. A 
ravelin is a triangular work, resembling the 
point of a bastion with the flanks cut off. 
See Fortification. 
Its use before a curtin is, to cover the oppo- 
site flanks of the two next bastions. It is 
used also to cover a bridge, or a gate, and is 
always placed without the moat. There are 
also double ravelins that serve to cover each 
other; they are said to be double when they 
are joined by a curtin. 
RAVEN. SeeCoRvus. 
RAUWOLF IA, a genus of the pentan- 
dria monogynia class of plants, the corolla of 
which consists of a single funnel-fashioned 
petal, with a large limb, divided into five 
ianceolatcd segments ; the fruit is a succulent 
berry, with two seeds. There are four spe- 
cies, trees of South America. 
RAY, a beam of light emitted from a ra- 
diant or luminous body. See Optics. 
Rays of light, colour and heat. of. Dr. 
Herschel had been employed in making ob- 
servations on the sun by means of telescopes. 
To prevent the inconvenience arising from 
the heat, he used coloured glasses ; but these 
glasses, when they were deep enough colour- 
ed to intercept the light, very soon cracked 
and broke in pieces. This circumstance in- 
duced him to examine the heating power of ; 
the different coloured rays. He made each 
of them in its turn fall upon the bulb of a 
thermometer, near which two other thermo- 
meters were plated to serve as a standard. 
The number of degrees which the thermo- i 
m*. ter exposed to the coloured ray rose above j 
the other two thermometers, indicated the 
heating power' of that ray. He found that 
the most refrangible rays have the least 
heating- power; and that the heating power 
gradually increases as the refrangibility di- 
minishes. The violet ray therefore has the 
smallest heating power, and the red ray the., 
greatest. Dr. Herschel found that the i seat- 
ing power of the violet, green, and red vays r 
are to each other as the following numbers : 
Violet = 16 
Green — 22.4 
Red = 55 
It Struck Dr. Herschel as remarkable, that'; 
the illuminating power and the heating power 
of the rays follow such different laws. The 
first exists in greatest perfection in the mid- 
dle of the spectrum, and diminishes as we 
approach either extremity ; but the second 
increases constantly from the violet end, and 
is greatest at the red end. This led him to 
suspect that perhaps the heating power does 
not stop at the end of the visible spectrum, 
but is continued beyond it. He placed the 
thermometer completely beyond the boun- 
dary of the red ray, but still in the line of 
the spectrum ; and it rose still higher than it 
had done when exposed to the red ray. On 
shifting the thermometer still farther/it con- 
tinued to rise; and the rise did not reach its 
maximum till the thermometer was half an 
inch beyond the utmost extremity of the red 
ray. When shifted still iarther, it sunk a 
little; but the power of heating was sensible 
at the .distance of If inch from the red ray. 
These important experiments have been 
lately repeated and fully confirmed by sir 
Henry Englefield, in the presence of some 
very good judges. The apparatus was very 
different irom that of Dr. Herschel, and con- 
trived on pin pose to obviate certain objec- 
tions which had been made to the conclusions 
drawn by that illustrious philosopher. T he 
bulbs of the thermometers used were mostly 
blackened. The following table exhibit's 
the result obtained in one of these experi- 
ments : 
Thermometer in the blue 
in 
3' from 
55° 
to 56’ 
green 
3 
54 
58 
yellow 
3 
56 
62 
full red 
C) I 
^ 1 
56 
72 
confines of red 24 
58 
735- 
the visible lig 
lit 2-| 
61 
4- 
79 
The thermometer with its bulb blackened 
rose much more when placed in the same cir- 
cumstances, than the thermometer whose 
buib was either naked or whitened with 
pah t. This will be apparent from the fol- 
lowing table: 
Redray - - S^k th L erm 
£v\ hite therm. 
Time. 
S' 
from 
58° 
55 
To 
61° 
58 
Dark - - - $ Black themi. 
59 
1 White therm. 
58 
58 $ 
Confines of red 5 th L ern ’ • ' 
( vv lute therm. 
3 
59 
574 
71 
60 | 
■ --- v oil ijuny tiisie- 
field take notice ot a faint blush of red of a 
semi-oval form, visible when the rays beyond 
the red end ot the spectrum were collected 
by a lens. 
From these experiments it seems to follow 
that there are rays emitted from the sun* 
which produce heat, but have not the power 
of illuminating; and that these are the rays 
which produce the greatest quantity of heat 
Consequently caloric is emitted from the si r 
§ 
