D E R 
tri£t of Chateau-Briant: twelve miles weft of Chateau- 
Briant. 
DERVEN'TIO, in ancient geography, a river of the 
Bjigantes in Britain : now the Derwent, in the eaft ot 
Yorkfhire, falling into the Oufe. Alfo a town of the 
Brigantes on the fame river : now Auldby, feven miles 
from York, to the north-eaft. Camden. 
DERVER A'GH, LOUGH, a lake of Ireland, in the 
county of Weft Meath : five miles north of Mullingar. 
DER'VIS, Dervich, or Dervish, J. \_Dervis, Er. 
from the trrn Perfian, a beggar.] A general name tor 
the priefts or monks of the Mohammedan religion in 
Turkey. There are thirty-four orders of dervifhes, whole 
monadic aufterity refembles that of the monks and her¬ 
mits in the Greek and Roman churches. Hadji Becktalh, 
in 1563, was the inftitutor of the itinerants , from whom 
the other orders have fprung. The howling or barking 
dervifhes are lo called from their rapid and incellant 
pronunciation of “ullah-hoo.” The Mevleveh dervifhes 
perform weekly a public worfhip, which confifts of danc¬ 
ing and turning on one foot with incredible rapidity, 
vvhilft a red-hot iron is held between the teeth. Totally 
exhaufted by pain and fatigue, they fall to the ground in 
3 fenfelefs trance, w hen they are removed to their cham¬ 
bers, and nurfed with thegreateft care, till their recovery 
enables them again to repeat fo fevere a difeipline. In 
this ceremony they are accompanied with the fofteft nni- 
fic, produced by the neh, or traverfe flute, the fantoor 
or pfalterv, and the tamboor or guitar. This practice, 
we are fold, is in memory of Mevleveh their patriarch’s 
turning miraculoufly round for theTpace of four days, 
without food or nourifhment, his companion Hamfa 
playing all the while on the flute ; after which he fell 
into an ecftaiy, and therein received wonderful revela¬ 
tions for the eftablifhment of his order. 
DER'UNCIN A'TION,/! A cutting off bullies, trees, 
er any thing encumbering the ground. 
DER'WENT, a river of England, in the county of 
Cumberland, which riles about iix miles fouth from Kef- 
wick, and runs into the Irilh fea, near Workington. 
DER'WENT, a river of England, which runs into 
the Oufe, five miles fouth-eaft of Selby, in the county 
of York. 
DER'WENT, a river which rifes in Northumberland, 
divides that county from Durham for feveral miles, when 
it crolfes a fmall part of the latter county, and enters the 
Tyne, about three miles above Newcallle. 
DER'WENT, a river which rifes in the northern part 
of the county of Derby, and, palling through the county, 
joins the Trent, eight miles eaft-fouth-eaft from Derby. 
DER'WENT FELLS, a mountain in the county of 
Cumberland ; celebrated -for its mines of black lead, a 
little to the fouth of Kefwick. 
DER'WENT WATER, a lake in the county of 
Cumberland, formed by the river Derwent, about four 
miles long, and more than one mile wide, with feveral 
fmall iflands, one of which is called Derwent: the north¬ 
ern part of the lake is very near Kefwick. Pennant ob- 
ferves that this lake is fubjeCt to violent agitations, and 
often without any apparent caufe, except what the peo¬ 
ple in the neighbourhood call a bottom wind. Dalton fays 
Derwent lake is agitated at certain times during a calm 
feafon, by fome unknown caufe. Mr. Croffthwaite has 
been affiduous in obferving every chcumftance that might 
lead to a difeovery of the caufe ; but his refult is, that 
nothing has occurred yet to throw light on the fubjeLt, 
He then gives various dates when the lake was difturb. 
ed; aroongft the reft he fays: “ Auguft 9, 1789, the 
lake was in very great agitation, w hite breakers upon 
large waves, See. without wind, October, 1792, the 
water again much agitated,” A correfpondent of the 
PhUofophical Magazine, in vol. xi. p. 164, relates the 
following particulars as the relult of his endeavours to 
inveftigate the caufe of this natural curiofity of our own 
Vol, V, No, sn. 
D E R 749 
country, which he attempted in October iSot. “ My 
boatman, named Walker, fays he has frequented the lake 
for about twenty-feven years, and heard of, perhaps, 
thirteen iflands, though previous to that time for twenty 
years none had appeared. One rofe in the year 1800, 
and two this year, iSot, which came up within two days 
of each other. The firft rofe the 1 ith of September, and 
part funk the 27th of the fame month. Sometimes one 
comes up and is down again in twenty-four hours, and 
fometitues they ftay two months. One of them, in 1798, 
was 180 yards long, fifty yards wide, and fluid at the top 
of the water fix weeks. One was pierced, and found 
feven yards thick. They frequently burft, and are rent 
fo wide, that boats can fail up and land paffengers at the 
edges of them, to walk about on the ifiand. One was a 
foot high perpendicular of land above the level of the 
water. They are connected always by one fide to the 
graffy turf at the edges of the lake. When, within a few 
days after their firft appearance, a pole is run three to 
fix feet into them, and drawn out again, the air for feve¬ 
ral feconds bubbles up like a pot boiling violently ; a 
fmell arifes like gunpowder, and it has been (aid that 
with a candle you might light a bottle-full that was 
once collected. I was this day rowed to one, a part of 
which continued above the water, which gradually deep¬ 
ened all round it, and found it of an oval fhape, about 
ten yards by five yards. The top was a fine firm mud, 
thick fet with a young aquatic plant. We puftied the 
boat-hook about four feet into it. The firft part, about 
two feet, appeared all mud, then lefs firm, and full of 
partially-decayed leaves and roots of trees and plants ; 
the water bubbled up for a few feconds about two inches 
high, occalioned by the air that followed the hook out. 
The riling of thefe iflands is always accompanied with a 
bottom wind ; yet the bottom wind appears frequently 
without them ; and generally after a month or fix weeks 
of dry weather the lake is fometimes partially, fome- 
times wholly, agitated, accompanied by a roaring noife, 
(the probable effects of echo in a calm in that fituation). 
The waves are not long and rolling, but irregular fliaped 
like mountains, twenty inches to two feet in height, like 
water jumbled in a tub ; they frequently ftrike the boat 
like a rock, and break in fpray from head to ftern, not 
always when it is perfectly calm, but alfo with a gentles 
breeze, barely enough to ripple the furface. They fre¬ 
quently indicate a change of weather from fair to rain, 
and the greateft degree of agitation is always in the deepeft 
water. Having thus minutely deferibed all the particu¬ 
lars I have time to collect, I fhall leave it to others to 
find a better explanation than the following: When we 
conlider that half the bottom of the lake is covered with 
a fine mud, impervious to air, refting upon half-putrid 
vegetable matter; that being attached to the Hoping 
banks, all air that is generated will endeavour to rife to 
the higheft part, but cannot then get out; that great 
part of the bottom is a clean bed of pebbles and (tones 
pervious to air; that the iflands begin to rife generally 
in from nine to twelve feet water, and are of confiderable 
furface ; that they have been meafured twenty-one feet 
thick, with clear water under them; and that the molt 
violent eftedts have been in the hummer months ; is it 
not probable that the air, fet at liberty by putrefaction, is 
enough to raife thefe large maffes, fo thick, and fo'little 
heavier than water it felt'; to contract and expand their 
extremities enough to give the violent and irregular mo¬ 
tion to the fuperincumbent waters, by their flowing off, 
their reflux, and their breaking through ; and that, more 
or lefs, whether they rife to the furface, or only part of 
the way, to find their equilibrium in the furfounding 
fluid ?” This is fuggefted as an inducement to others 
to inveftigate the caufe of this Angular phenomenon. 
DE'RY, a river of Wales, in the county of Merioneth^ 
which runs into the Avon, near Dolgeily, in Merion. 
ethlhire. 
DESAGUE- 
