S P I 



S P I 



be diftinguiftied by the fame trial, by its yielding a mucTi 

 finer and thinner fmoke, and burning with a bright blue 

 flame. If they be- tried by firing them in a fpoon, that 

 which is adulterated with fpirit of wine will burn very 

 bright, and yield no fume at firft ; but as it grows near the 

 bottom it will fmoke a little, and finally will leave no refi- 

 duum, except that it varnifhes over the infide of the fpoon : 

 that adulterated with the oil of turpentine will burn more 

 vehemently, fmoke more, and leave a coarfer varnifh upon 

 the fpoon ; and if it be of the coarfefl kind, that is, if it 

 hath been adulterated with badly reftified oil of turpentine, 

 the fume vrill be the more abundant, and there will be left 

 in the fpoon a fetid matter, refcmbling melted pitch. 



Mr. Geoffroy tried whether, in the bufinefs of varnifhing, 

 the oil of turpentine alone might not do as well as the oil 

 of fpike ; he found that it dried perfeftly well, but that it 

 left a (linking fmell upon the work, which never went off ; 

 whereas the mixture of this oil with that of fpike, makes 

 a fmell like neither, and which loon goes off. 



An ounce of oil of turpentine, with only twenty drops, 

 either of our common oil of lavender, or the pure oil of 

 fpike, makes a liquor tolerably well fcented, and which 

 ferves for the purpofes of oil of fpike. If two drachms of 

 our oil of lavender be added to fix drachms of fpirit of 

 wine, they immediately mix ; and this, afterwards mixed in 

 a fmall proportion with oil of turpentine, makes a fort of 

 oil of fpike. 



The moft regular method, however, that the artificer can 

 ufe, if he can get the genuine oil of fpike, is to mix one ounce 

 of it with three ounces of oil of turpentine, which perfeftly 

 fits it for this purpofe, and makes it the fame with that in 

 common ufe. The method of making this perfeftly pure, 

 13 to rediftil it in a balneum Mariae ; there will thus be pro- 

 cured an oil highly reftified, and pellucid as water, which 

 will dry away as foon as touched on any thing. The great 

 difadvantage attending the oil of fpike adulterated with 

 fpirit of wine is, that it will not readily mix with all the 

 forts of varnilh. 



Having gone through the properties of oil of fpike, in 

 regard to varnifh, it remains to inquire into them in regard 

 to its other great ufe in enamel, and to confider the effefts of 

 the two ufual methods of adulterating it in this work. 



The oil of fpike which wants body, is not at all fit for 

 enamelling, becaufe it dries too fuddenly, and does not at 

 all affift the natural drynefs of the enamel, which is only a 

 fort of powder of glafs ; and the particles of this powder, 

 with a fluid of too little body, are not manageable by the 

 artifts, fo that the colour never is brought to a due con- 

 fiftence ; and when the oil has too much body, the mixture 

 becomes too tenacious, and is as unmanageable in that ex- 

 treme as in the other ; and this fault is attended with 

 another very great mifchief, which is, that the fume raifed 

 by this oil, when heated, is often fo grofs, as to deftroy the 

 beauty of the colours. In fliort, thick oil of turpentine is 

 always deftruftivt of enamels by its fmoke. 



The true compofition for enamelling is oil of fpike mixed 

 with fpirit of wine, but the proportions mull be nicely re- 

 gulated from repeated trials : for if the quantity of the 

 fpirit be too large, it is apt to feparate itfelf from the oil 

 and colour in the drying, and this always fpoils the glofs 

 and beauty of the work. Artificers obferve, that oil of 

 fpike does beft for their purpofes, after it has been kept 

 two or three years. But this is only owing to the oil's 

 being adulterated with fpirit of wine, and ufually contain- 

 ing too large a proportion of the fpirit when firlt fent over : 

 it becomes better for ufe when a part of that fpirit has had 

 time to evaporate in the keeping. It would be a better 



4 



way for thefe curious works, to procure the oil pure, and 

 then occafionally mix it with fuch a proportion of fpirit of 

 wine, as experience (hews to be the moll proper. Mem. 

 Acad. Par. 1716. 



Spike, La-vender. See Lavender. 



Spike, Winged, Grafs, in Botany. See Stipa. 



Spike, Hand, in Mechanics. See W.WiT)- Spike. 



Spike a Gun, in Military Language, fcfc, fignifies to 

 choak up the touch-hole of a piece of ordnance, fo as to 

 render it ufelefs. See Nail. 



SpiKE-Roller, in jigriculture, a very ufeful implement of 

 the roller kind, firft introduced by Mr. Randall of York to 

 the notice of the farmer. It has been found of much ad- 

 vantaoje in bringing itifF cloddy lands into a ftate of fuitable 

 pulverization and finenefs ot mould for being fown. It is 

 likewife employed, in a beneficial manner, on fward-land 

 that is worn out and mofly, by preparing it for the apphca- 

 tion of earthy compofts and grafs-feeds. But it is remarked 

 by the inventor, that in this bufinefs the roller muft go up 

 and down, till the fwarth and ground are perfeftly well 

 broken up : this being done, the feeds of clover, trefoil, 

 and rye-grafs, or any other mixed with them, muft be fown 

 in the ufual way and quantity ; then the compoft muft be 

 fpread over the feeds, fo as to cover them ; and a common 

 barley-roller, with a thorn-bufti fattened to it, muft follow, 

 and the ground be ftiut up, left the cattle ftiould do harm 

 by treading. v 



In refpeft to this fort of roller, the dimenfions in length 

 were feven feet, the diameters at the ends eighteen inelies, 

 and the whole cylinder made of the heart of oak ; and when 

 the irons were burnt in, and the man feated on the box de- 

 figned for that purpofe, the weight of the whole was about 

 a ton. But the blunt ends of the irons were oppofcd to the 

 clods, and run more taper, till they came to the furface of 

 the cylinder, into which the irons were burnt, and inferted 

 about three inches, which was their length above the furface 

 of the roller, and which he always found very fufGcient to 

 crufti the hardeft clod that ever came in their way. Had he, 

 indeed, attempted to go on the ground, when the foil was 

 not perfeftly dry, this pofition of the irons would have carried 

 the clods round with the roller ; for it is not its province to 

 fqueeze, but crufti. Nor indeed can a man do more harm 

 to his ground than going upon it, when it is not quite dry, 

 with a roller conftrufted in this way. He had the irons 

 fixed in four inches afunder, in the firft row, from end to 

 end. The fecond row began juft between the firft and fe- 

 cond irons of the firft row. The third row was like the 

 firft ; and the fourth like the fecond. Then alternately for 

 the whole furface of the cylinder, as near as poflible, the 

 irons were four inches afunder in each individual row ; and 

 four inches from row to row, as nearly as the fuperficies of 

 the cylinder would permit. He does not know how to con- 

 vey ajufter idea of the Ihape of the irons than to call them 

 ox-harrow teeth, or thofe of a very large harrow ; for when 

 he fent for the workman, he defired him to make fo many 

 of this denomination, fix inches in length, and burn the 

 fmall end three inches into the wood. This is a roller that 

 requires a ftrong team in performing its work. 



But in addition to thefe ufes, it has been fuggefted that it 

 may likewife be very ufeful in preparing clay for the making 

 of canals, or pieces of water : for where, as fometimes hap- 

 pens, the clay grows dry, and will not admit of being duly 

 tempered for ufe, without great pains in breaking it, a very 

 large quantity may very foon be reduced to the requifite 

 finenefs, by fpreading it on hard ground in a due thick- 

 nefs, and pafiing this roller a few times over it. In exten- 

 five works, much trouble and labour may fometimes be 



faved 



