M U R E X. 
21(5 
6. Murex potman: fliell ovate, knotty, with protube¬ 
rances from three to ieven ; beak broad. It inhabits the 
eaftern Ihores of Africa; is coarfe and ponderous. 
7. Murex decuflatus: fliell ovate, tranfverfely grooved, 
with convex ribs, croffed by perpendicular knots ; beak 
imperforate. Found on the eaftern coalls of Africa. The 
margin of the lip of this fpecies is membranaceous; the 
l'pire has feven diftindt whorls. 
8. Murex triacanthus : Ihell turgid, knotty, tranfverfely 
ftriate, with a triple row of fpines. Found in a follile 
ftate; fliell fliaped like a fig, with five or fix horizontal 
belts crofling the ftrias; beak above an inch long; the 
three outmoft whorls knotty, and a little prominent. 
9. Murex melanamathus: fliell tranfverfely ftriate, with 
eight rows of hollow black fpines; fpire a little knotty 
and prickly; beak fubulate. The place of its habitation 
is not known. 
10. Murex radix: fliell white, with numerous rows of 
frondofe black undulate fpines. This is extremely rare, 
and its habitation not afcertained. 
11. Murex candidus: fliell white, with rows of fpines, 
and very fliort beak. The fliell is about two inches long, 
and fome of the fpines are black. 
ia. Murex fafciatus : the fliell of this fpecies is inflated, 
with rows of fpines, white barred with brown ; the fpire 
lias four diftinft turgid whorls. 
II. Sutures expanding into crifped foliations ; the beak is 
abbreviated .— Purpura; that is, the Jpecies of this divifion 
conjlitute the tribe of purple-fijh properly J'o called. 
Purple was much efteemed among the ancients-; efpe- 
cially the Tyrian purple, which underwent more dyes than 
the reft, and which was almoft peculiar to the emperors 
and kings. Yet this purple did not exceed that now in 
life. The chief reafons why the ancient purple dye has 
been difufed are, that the modern is both cheaper and finer. 
The method of obtaining the colour, Mr. Cole defcribes 
thus: The fliell, which is very hard, being broken, (with 
the mouth of the fifli downwards, fo as not to cruftt the 
body,) and the broken pieces being picked off, there ap¬ 
pears a white vein lying tranfverfely in a little furrow or 
cleft next the head of the fifli. In this vein is the purple 
matter lodged; fome of which, being laid on linen, ap¬ 
pears st firft of a light green colour; and, if expofed to 
the fun, foon changes into a deep green, and, in a few 
minutes, into a lea-green, and, in a few more, into a 
blue; thence it foon becomes of a purplilh-red, and, in 
an hour more, of a deep purple-red. And here the fun’s 
aftion terminates ; but by wafliing in fcalding water and 
foap, and drying it, the colour ripens to a moft bright 
and beautiful crimfon, wdiich will bear wafliing admirably 
without the addition of any ftyptic. While the cloth 
marked with this colour lies in the fun, it will yield a 
very ftrong and foetid fmell, as if garlic and afia-fcetida 
were mixed together. _ 
The juice which gives this beautiful purple colour is, 
fays M. Duhamel, while it remains in the body of the 
animal, and while that is in health, wholly white; but no 
fooner is it expofed to the fun, than it begins to change 
colour, and in lefs than five minutes goes through the 
feveral changes of pale green, yellowilh, and a beautiful 
emerald green; after this it becomes of a deeper and 
dulkier green, then bluilh, reddifti, and finally a deep and 
very beautiful purple. Sometimes the juice is found na¬ 
turally green in the animal: this is probably from the 
creature's being in a difeafed ftate; but, when it is natu¬ 
rally thus, it immediately becomes red, and afterwards 
purple, on being expofed to the fun; its feveral preceding- 
changes feeming to have been made already in the body 
of the animal, if a piece or linen be rubbed over with 
this juice, and part of it expofed to the fun, part not, that 
only will turn red which is fo expofed, the other remain¬ 
ing green without any alteration; and it is obferved, that, 
the itronger the fun fliines, the quicker the change ap¬ 
pears, and probably the colour is in proportion alio the 
more beautiful and lively. And it is very remarkable, 
that, if a needle, or any other opaque body, be laid upon 
the linen which is yet green, and is to become red on 
being expofed to the fun; after fuch an expofure, the 
whole fiiall be changed red or purple, excepting only that 
fmall fpot which is covered by the needle, which will ftill 
remain green. A plate of glafs, though it be three inches 
thick, will not prevent the colour from changing purple 
by being laid over it; but the thinneft piece of metal will 
keep it wholly green. The one being opaque, and the 
other pellucid, are evidently the only reafons for this dif¬ 
ference. If the coloured linen be fuccelfively covered by 
three pieces of paper, the one blacked with ink, the other 
in its natural ftate, and the third rubbed over with oil, it 
will change colour on being expofed to the fun in diffe¬ 
rent degrees; and that exaftly in proportion to the de¬ 
gree of tranlparence in each of the papers: moft of all 
in that which was covered with the oiled paper; fome- 
thing lefs in that covered by the paper in its natural 
ftate; and leaft of all in that which was covered with the 
blacked paper, as that is leaft tranfparent. The common 
heat of a fire, or that of a red-hot iron, produces no change 
at all in the colour when green. The vapour of burning 
fulphur produces a little; but the green, which had not 
changed to purple by thefe experiments, immediately 
changed to it on being expofed to the rays of the fun. 
Thefe experiments were all made in the months of Ja¬ 
nuary and February, by M. Duhamel, in Provence ; and, 
the fun having power to change the colour fo fpeedily 
there in thefe cold months, probably in a warmer climate 
or feafon the air would have been fufficient for the pur- 
pofe, without the open fun ; fince it feems, from experi¬ 
ment, that both the folar rays, and the light alone in a 
cloudy day, can aft upon this colour. The light and 
heat of the fun both aft on this colour: light is always 
fufficient to produce the effeft, but the heat may eafily 
be too great or too little; and, to do the whole in per- 
feftion, it muft be at a certain middle degree. 
This beautiful purple, if it fhould ever be brought into 
ufe in dyeing, will have one very great advantage from 
its vifcofity. The pieces of cloth that had been ftained 
by it retained their colour, in fpite of feveral boilings in 
different liquors, which M. Duhamel made them pafs 
through; and the colour, on examination, was found not 
to be luperficial, but penetrated the whole body of the 
fluff, which was tinged by it. There are many inconve¬ 
niences which muft naturally attend the ufe of this fub- 
ftance as a dye; but they may, perhaps, all be got over by 
care and application. It is very certain, that it is of too 
vifcid a nature eafily to penetrate many fubftances; but 
it is alfo certain, that this might be obviated by diffolv- 
ing it in fome proper liquor. It appears very plainly, that 
the ancients had a method of thus diffolving their purple j 
but we neither know what was their purple, nor what 
was its dilfolvent; nor, which would be of much more 
confequence to us at prefent, what is the proper diflolvent 
for our own. Mem. Acad. Scien. Par. 1736. 
Other fpecies of fifli, as well as the Murex, ferved 
among the ancients to dye the fine purple colour they 
were lb fond of, and fome of the Euccina (e. g. the B. la- 
pilius of Linnaeus) have been of late found to have the 
lame juice. But the fmall quantity of the coloured juice 
which each fifli contains, and the neceflity of ufing it be¬ 
fore the animal dies, makes it impolfible to bring it to 
any regular article of traffic. The ancients ufed this co¬ 
lour only on cotton and woollen Hulls; whereas our co¬ 
chineal, which was unknown to the ancients, ftrikes 
equally well on filks and ftuffs. See the article Dying, 
vol. vi. p. 140, 1. 
13. Murex ramofus: ftiell with a triple row of folia¬ 
tions and contiguous fpire; beak truncate. The fliell is 
tranfverfely ftriate,'varying much in lhape, colour, and 
appearance, of the foliations. 
14. Murex 
