VAR 
£ 4- They own that as the coloured body is not imme- | 
diately applied to the organ to occafion the fenfation, 
as no body can affect the ienfe but by immediate Con- 
tad:, the coloured body does not excite the fenfation 
of itfelf, or contribute any thing to k, otherwife than 
by moving fome interpofed medium, and by that the 
organ of fight. 
15. They add, that as it is found that bodies do riot ^ 
affed the fenfe in the dark, and that light only occa- 
fions the fenfation of colour, by moving the organ ; 
and that coloured bodies are no farther concerned than 
in reflecting the light in a certain modification ; the , 
difference in colours, according to them, arifes in a 
difference in the texture of their parts, by which they 
are difpofed to refled their light with this or that mo- 
dification. 
1 6 . Dr. Hook, in his Micographia fays. The phan- 
tafm of colours is caufed by the fenfation of the ob- 
lique or uneven pulfe of light, and that this is capa- 
ble of no more varieties than two, which arife from 
the two fides of the oblique pulfe ; fo that there are 
in reality but two Ample colours, yellow and blue ; 
from the mixture of which, and a due proportion of 
black and white (that is, darknefs and light) dll colours 
may be be produced. 
17. But this phenomenon of nature and colour, hav- , 
ing long perplexed philofophers to account for the dif- 
coveries relating thereto, the incomparable Sir Ifaac 
Newton found by two experiments on prifms, that 
there is a great deformity in the rays of light, and 
that hereby the origin of colours may be unfolded. 
The dodrine of colours therefore, according to his 
notion and experiments, are contained in the follow- 
ing propofitions : 
1. That light confifts of an infinite number of rays, 
right lined and parallel, but of different degrees of 
refrangibility, when meeting with a different me- 
dium. 
2. Each ray, according to its degree of refrangibility, 
when fo refraded, appears to the eye of a different 
colour. 
3. The leaft frangible rays appear of a deep fcarlet 
colour ; the moft refrangible appear of a Violet blue 
the intermediate proceeding from fcarlet to yellowifti, 
then to light green, and fo to blue. 
4. The colours arifing from the different degrees of 
refrangibility of light are not only the more noted co- 
lours of red, yellow, green and blue, but alio all the 
intermediate colours of red to yellow, of yellow to 
green, &c. 
5. Whitenefs, (fueh as the fun’s light appears,) Con- 
taining all thofe degrees of refrangibility, is confe- 
quently made up of all the above-mentioned colours. 
6. Simple or homogeneal colours, are fuch as are 
produced by homogeneal lights or rays, which have 
the fame degree of refrangibility ; and mixed colours 
are fuch as are produced by rays of different refrangi- 
bility. 
7. Rays of the fame refrangibility produce the fame 
colour ; which colour is not alterable by repeated re- 
fractions, but only made ftrong or faint, as the rays 
are united or fcattered. 
8. All bodies appear of this or that colour, according 
as their furfaces are adapted to reflect only the rays 
of fuch a colour : or at leaft in more plenty than the 
reft. 
But to explain thefe things farther : 
It is found by experience, that rays or beams of light 
are compofed of particles very heterogeneous or dif- 
fimilar to each other ; i. e. fome of them, as it is 
highly probable, are larger, and others lefs ; for a ray 
of light, being received on a refracting furface in a 
dark place, is not wholly refraded, but fplit as it were, 
and diffufed into feveral little ravs 1 fome of which 
are refraded to the extreme points, and others to the 
intermediate points •, i. e. thofe particles of the light, 
which are moft minute, are diverted the moft eafily 
and moft confiderably of all others, by the adion of 
the refrading furface, out of their redilineal courfe ; 
. • VEG 
and the reft, as each exceeds another in magnitude., 
fo it is turned out of its right line with much diffi- 
culty, and Ids confiderably. 
Now each ray of light, as it differs from another in 
its degree of refrangibility* fo likcwile it differs from 
it in colour. This is warranted by numerous experi- 
ments, 
Thofe particles which are more refraded, are found 
to conftitute a ray of a Violet colour * i. e. in all pro- 
bability, the moft minute particles of light, thus fe- 
parately impelled, excite the fliorteft vibration in 
the retina, which are thence propagated by the folid 
fibres of the optic nerve into the brain, there to excite 
the fenfation of Violet colour, as being the moft dufky 
and languid of all colours. 
Again : thofe particles which are the moft refraded 
conftitute a radiolus, or little ray, of a red colour j 
i. e. the largeft particles of light excite the longeft vi- 
brations in the retina, fo as to excite the fenfation of 
red colour, the brighteft and moft vivid of all colours. 
It is remarkable, that in the growing of plants, the 
fame plants do from time to time, alter and change 
their colours as the veffels which are in their youno- 
{hoots grow larger. The leaves are of a faint yellow 
when they are in their fmaller ftate, but they become 
of a bright green, or fometimes red, when they are in 
their middle ftate ; but when their veffels are enlarged 
to their full growth, they become of a dark green, and 
then change to a feuillemort colour towards autumn, 
from the ripening of their juices ; from thence to pu~ 
trefadion, which refolves itfelf again into earth, its 
firft principle. 
VASCULIFEROUS PLANTS are fuch whofe 
feeds are contained in veffels, which are fometimes di- 
vided ; and thefe have always a monopetalous flower, 
either uniform ordifform. 
VASES: A Vafe is a fort of a flower-pot to fet in a 
garden. 
VEGETABLE, a term applied to all plants, con- 
fidered as capable of growth ; i. e. to all natural bo- 
dies, which have parts organically formed for gene- 
ration and accretion, but not for fenfation. 
Dr. Boerhaave defines a Vegetable to be a body gene- 
rated of the earth, to which it adheres, and is con- 
neded by parts called roots, through which it receives 
the matter of its nourifhment and increafe, and con- 
fifts of juices and veffels, fenfibly diftind from each, 
other ; or a Vegetable is an organical body, compofed 
of veffels and juices every where diftinguifhable from, 
each other, to which the roots grow, or parts by which 
it adheres to fome other body, from which it derives 
the matter of its life and growth. 
This definition of a Vegetable is very fcientific, and 
furnifhes us with a juft and adequate idea of it; for 
by its confiding of veffels and juices, it is diftinguifhed 
from a fofiil ; and by its adhering to another body, 
and deriving its nourishment therefrom, it is diftin- . 
guifhed from an animal. 
He defines a Vegetable an organical body, becaufe it 
confifts of different parts, which jointly concur to the 
exercife of the fame function. 
The definition of its adhering by fome of its parts to 
another body is very proper ; for we know of no plant 
that is fo abfolutely vague and fluctuating, but has 
{till a body it adheres to, though that body may be 
various, e. g. earth, as in our common plants ; ftone, 
as in rock plants ; water, as in fea plants ; air, as in 
fome mucilages. 
As to thofe few plants that appear to float with the 
water, their manner of growth is fcmewhat anoma- 
lous. Monfieur Tournefort has fhewn, That all plarits 
do not arife ftriCtly from feeds ; but that fome, inftead 
of femen, depofit or let fall a drop of juice, which 
finking in the water by its gravity, reaches the bottom, 
or fome rock, &c. in its way, to which it flicks, 
ftrikes root, and (hoots into branches : fuch is the 
origin of coral. 
To which may be added, That a root of a plant rffay 
have any fttuation at pleafure, with refpeCt to the 
body 
