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metals to be tinned, and the oily matter contained in it 

 funiifhcs the phlogiftoQ (accordinjr to the old fyftem) that 

 is nccclTary in this operation. Tlic copper, or brafs, being 

 made hot eiiough to melt tin laid upon it, is llrewed over with 

 fal anmioiiiac, and the melted tin rubbed about the plate. 

 The fal ammoniac takes up the drofs of the tin, and leaves 

 the tin to flow freely upon the metal. As the furface of cop- 

 per is continually altered by the mere attion of the air, the 

 workmen, before the tinning of any veflel, fcrapc its furface 

 with a ftcel inftrument till it be clean and bright ; then they 

 place the veffel upon kindled coals, and heat it to a certain 

 degree : as foon as it is hot, in fome proceffes of tinning, 

 they rub it with pitch, and apply the melted tin, which 

 they fpread upon the furface of the copper by means of 

 hai'ds. For this pui'pofe pure tin is feldom ided ; but, 

 in general, two parts of tin are alloyed with one part of lead. 



The pitch ufed in this latter mode of tinning is quite 

 neceffary, becaufe the degree of heat given to the copper 

 is fufficient to calcine its furface in fome degree : and this 

 alteration, however flight, would prevent the perfect adhe- 

 fion of the tin, unlefs by means of the pitch the phlogifton 

 was reftored to it at the very inftant of the application of 

 the tin. The pitch alfo prevents the (light calcination 

 which would happen on the furface of the tin, or revives 

 the fmall particles of calx which are formed during the 

 operation. In either way, or in the method of tinning iron 

 plates, the fuccefs of the operation depends on the faciUty 

 with which tin unites with thefe metals, which incorporates 

 with them, diffolves in fome meafure their furface, and forms 

 a kind of alloy, at leaft when the tinning is well perfonned ; 

 and moreover, on the cleannefs of the iurfaces, both of the 

 melted tin, and of the copper or iron to which it is applied ; 

 for the metals cannot perfedlly unite unlefs they are in a 

 metallic ftate, and free even from their own earth or calx. 



It has been alleged that copper veflels, fo pernicious 

 in themfelves, are not perfeftly preferred from ruft or ver- 

 digris by tinning ; and, befides, tin itfelf is combined with 

 arlenic, and lead is alfo ufed in tinning. M. Malouin has, 

 tUerefore, propofed in his Memoirs on Zinc (Mem. de 

 I'Acad. Sc. 1742.) to fubftitute that femi-metal in place 

 of lead and tin, for the tinning of iron and copper velFels ; 

 the greater hardnefs of the zinc, it is thought, would render 

 it lels hable to be worn, and the dangerous efFecls of lead and 

 tin would be avoided. Macquer's Dift. Chem. Engl. edit. 



The plumbers, on fome occafions, tin or whiten their 

 fheets of lead : in order to which they have a tinning furnace, 

 filled with live coal, at the two fides of which two men are 

 placed, who hold up the fheets over the fire to heat : and 

 tlic tin-leaves being laid over them, as faft as the fhects grow 

 hot, and the tin melts, they fpread it, and make it take by 

 rubbing it with tow and refin. 



TINNITUS AURIUM. A very common difeafe in the 

 fenfe of hearing, is when certain founds, like thofe of a drum, 

 a bell, the falhng of water, &c. are heard, wlien no fuch 

 noifes aaually exift, or can be heard by other perfons. 

 This affeftion is called tinnitus aurium, of which vainous kinds 

 have been obferved. For the moil part, it is a very (light 

 tranfient diforder ; but fometimes it is molt obftinate, long 

 contmued, and troublefome. It fometimes arifes from the 

 flighteft canfe, fuch as any thing partially (lopping up the 

 meatus auditorius, or Euftachian tube itfelf, fo that the free 

 paffage of air into the cavity of the tympanum is inter- 

 rupted. A kind of tinnitus is heard by the moil healthy 

 •when they yawn. 



A much more frequent and troublefome fpecies of tin- 

 intus accompanies many difeafes both of the febrile and 

 ucrvous kind. This is faid to be occafioned partly by the 



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increafed impetus of the blood towards the head, with an 

 increafe of fcnfibility in the nervous fyllem itfelf, fo that the 

 very beatings of the arteries are heard ; and partly by the 

 augmented irritabihty and fpafmodic motions of the little muf- 

 cles within the organ of he.iring. In fevers, the throbbing 

 of the carotid arteries at the fides of the fella turcica has 

 produced excelfive annoyantc in particular individuals, efpe- 

 cially when they were in the recumbent pofture ; and the 

 celebrated Haller informs us, that when he was afflifted 

 with fever, he fuffered much from the beating fenfation 

 caufed in his ears, as he fuppofed, from the pulfation of the 

 carotids in the neighbourhood of thofe organs. 



According to writers, tinnitus aurium fometimes arifes 

 from a vehement affeftion of the mind ; fometimes from a 

 diforder in the ftomach ; fometimes from rheumatifm ex- 

 tending its effefts to the ears and head ; or from a catarrh, 

 producing a temporary obftruAion in the Euftachian tube. 

 In the foregoing examples, the cure of the affeftion of the 

 ear depends upon the removal of the other diforders, of 

 which it is merely an effeft. 



In certain caics, tinnitus aurium occurs as a feparale 

 independent diforder, and may be the caufe of long-continued, 

 diftreffing fuffering. The exiftence of unreal founds in 

 the organ of hearing generally prevents the patient from 

 hearing diftinftly other fonorous impreifions, and, of courfe, 

 more or lefs deafnefs is a common attendant of the complaint. 



The writer of this article lately had a patient, who is 

 attacked five or fix times every year with tinnitus aurium, 

 which caufes for feveral days the moft annoying fenfations 

 in the ears, and a confiderable degree of deafnefs. The 

 diforder is always accompanied with fevere pain in the 

 branches of the nerve coming out of the infra-orbitary 

 foramen, head-ache, indigeftion, and many fymptoms of the 

 nervous and bilious kind. 



In this cafe, relief is obtained by fomenting the affedled 

 ear with a decoftion of'poppies, and wafhing out the meatus 

 auditorius with a fyringe and warm water. However, thefe 

 means are always afiifted with a few dofes of calomel and 

 rhubarb, without which, in all probabihty, the local appli- 

 cations would not entirely anfwer. 



We have alfo had other cafes, in which a ftrong folution 

 of opium in water, camphorated oil, bliilers, &c. were the 

 remedies employed. 



The tinnitus aurium, produced by fevers, fometimes 

 does not fubfide at their termination, but lafts, either in a 

 continued or periodical form, during life. Two fuch 

 inftances are now within our own recolledlion ; and every 

 man of experience muft have witneffed the fame thing. 



TINNUNCULUS, in Ornithology, the name of one of 

 the long-winged hawks, called by Linnseus Falco tinnun- 

 culus ; which fee. 



It is about the fize of a common pigeon. Its bill is 

 fhort, crooked, and very (harp, and covered with yellow 

 tlcin at the top ; near this the bill is white, elfewhere it is 

 blue ; its tongue is bifid ; its mouth very wide, and its 

 palate blue ; its head is large and flatted, and is of an a(h- 

 colour, with longitudinal ureaks of black ; its back and 

 wings are brown, variegated with black fpots ; its rump is 

 grey, with fome tranlVerfe black fpots ; and its bread and 

 belly of a pale ruft-colour, with a few longitudinal ftreaks 

 of black ; its tail is long and pointed, its tip of a pale fer- 

 ruginous hue, with a broad tranfverfe ftreak of black over 

 it ; and the reft of the tail is a mixed grey and brown, 

 with black fpots and ftreaks ; its legs and feet are of a fine 

 yellow. 



The tinnunculus, or keftrel, breeds in the hollows of 

 trees, in the holes of high rocks, towers, and ruinated 



buildings : 



