WOOL. 



the cafe ; a fleece grown upon the fame animal may be in- 

 creafed in weight either by the fibres becoming coarfer, or 

 by their being grown longer, or by a greater number of 

 fibres being grown in the fame flcin. To the wool-grower 

 it can never anfwer to increafe the weight of the fleece on 

 fmall fine-woolled flieep, by growing the wool coarfer ; if 

 this be his objeft, the long-wooUed breeds of ftieep are to 

 be preferred. He may produce wool fomewhat longer by 

 increafing the quantity of food ; but it generally lofes fome- 

 thing of its finenefs, and is lefs fuitable for the cloth trade. 

 He may, however, increafe the weight confiderably by fe- 

 lefting fuch breeds as grow the wool clofe upon the fkin, 

 and are thickly covered with wool over every part of the 

 body. In this refpeft, the Merino flieep have greatly the 

 advantage over any of the native breeds of Englifli flieep ; 

 many of them yielding from three to four pounds of pure wool, 

 whilft the fineft Englifli fleeces rarely exceed two pounds, and 

 would lofe one-fourth of this weight when brought to a pure 

 fl;ate by fcouring. It has been doubted whether all flieep's- 

 wool, when clean, poflefles the fame fpecific gravity ; but ad- 

 mitting there may be fome variation in the wool from different 

 piles, we conceive that it is too minute to deferve the atten- 

 tion of the wool-grower or manufafturer. 



The filaments of fine wool being fo minute, it requires 

 an eye habituated by long experience to appreciate the re- 

 lative finenefs of two piles, which may diff^er in value as 

 much as twenty-five per cent. Even thofe who have been 

 long praftifed in fuch examinations find it difficult to form 

 immediately a correft opinion of the finenefs, if they are 

 removed for a few weeks from all opportunity of viewing 

 wool. It is not furprifing then that the wool-grower, who 

 only direfts his attention to the fubjeft during one part of 

 the year, fliould often be unable to judge whether his wool 

 has improved or not fince the preceding fummer. On this 

 account it would be highly defirable that fome eafy and 

 correft method of admeafurement by the micrometer could 

 be invented, which might enable the obferver to decide this 

 with certainty. Mr. Daubenton employed a graduated 

 fcale, adapting it to the eye-piece of a compound micro- 

 fcope ; but his method does not admit of accuracy. Mr. 

 Luccock made ufe of a more fimple inftrument, which 

 we have feen ; it confifl;ed of a lens about half an inch 

 in focal length, adjufl;ed to a graduated fcale. On this 

 fcale a number of fibres were flretched and comprefled 

 by a Aider and fcrew into a given fpace ; the filaments 

 covering this fpace were then counted by the aid of the 

 lens, and a number of admeafurements being taken of 

 the fame fort, the mean of the whole was fuppofed to 

 give the correft diameter of the filament. In this me- 

 thod, however, fome of the filaments mufl: unavoidably 

 overlap part of the others, on which account a greater num- 

 ber will be feen in a given fpace than there would be were 

 the whole diameter of each fibre vifible. The error refult- 

 jng from this may be ftated at one-fifth. Thus Mr. Luccock 

 makes the belt Englifli wool to meafure the fourteen- 

 hundredth part of an inch, which is finer than the bed 

 Spanifti, as meafured by Dr. Parry, by a more accurate 

 but more laborioas method. According to Mr. Luccock, a 

 fample of moderately fine Spanifli wool reached to the 

 fixteen-hundredth part of an inch ; according to Dr. Parry, 

 the very beft Spanifti is not fmaller than the fourteen- 

 hundredth part of an inch. 



With the above deduftion of one-fifth, which we believe 

 to be a near approximation to correftnefs, the diameter of 

 the fibres of the beft; Englifli wool, as forted in the ufual 

 jnethod, will be nearly as follows : 



The method of meafurement adopted by Mr. Luccock 

 might be fufiiciently correft with the deduftion of one-fifth, 

 were the inft;rument always ufed by the fame perfon, and a 

 fimilar degree of preflure given in each experiment ; but as 

 this is required, it becomes uncertain in its refults, and 

 inadequate to praftical purpofes. 



Dr. Parry's method of meafurement is eft'efted with an 

 inftrument fimilar in principle to the lamp micrometer of Dr. 

 Herfchel, of which an account is publiflied in the Philofophi- 

 calTranfaftions for 1782. (See Micrometer. ) An objeft 

 of a known diameter being placed in the focus of a compound 

 microfcope, and ftrongly illuminated, a piece of white paper 

 is placed horizontally at fome diftance beneath it ; then 

 looking through the microfcope with one eye, and keeping 

 the other fteadily open, you will fee the objeft apparently 

 projefted on the paper, which is to be meafured, whilil 

 viewing it, with a pair of compafles. Divide the length of 

 the image fo meafured with the known diameter of the ob- 

 je<S, which will give the magnifying power of the micro- 

 fcope. This being found, place the objeft you wifli to 

 meafure in the focus, and projefting its image on the paper 

 as before, meafure it with the compafles, and divide the re- 

 fult by the magnifying power, which will be the real mag- 

 nitude of the objeft required. 



The light of a lamp is to be preferred to day-light, and 

 the fibres to be meafured are to hejlretched on a glafs, and 

 waxed down at both ends. The under fide of the glafs 

 ftiould be blackened with Indian ink, except in three parts, 

 the middle, and near the two ends. The unblackened fpaces 

 being placed in the focus of the microfcope, ten or more 

 filaments may be examined and meafured fucceffively, both 

 in the middle part of the glafs, and near the ends, which 

 will give the diameter of the filament at the upper and lower 

 end of the ftaple, and in the middle. Each lock of ten 

 filaments being thus examined in three diff'erent parts, the 

 mean of the three meafurements muft be taken for the mean 

 diameter of each filament, and the mean diameter of the 

 ten filaments may be taken for the finenefs of the whole 

 lock. 



In place of the blackened glafs, we would recommend a 

 thin Aide of ivory or brafs, about five inches in length, 

 and half an inch in breadth, with three tranfverfe flits or 

 openings, one in the middle, and the two otliers about 

 three-fourths of an inch from each end. On this Aide the 

 filaments may be ftretched, it will not be liable to break, and 

 the edges of the filaments will be more correftly defined 

 than when a plate of glafs is placed under them. 



The farther the paper is removed from the eye, the larger 

 will be the apparent fpace covered by the image of the 

 objeft, but it muft not be too far for the hand to meafure it 

 with compafles. But if in place of the compaffes we have 

 a flieet of pafteboard graduated into minute divifiong from a 

 black line upwards, and a Aiding index be adjufted, the 

 pafteboard may be placed at a much greater diftance, the 

 obferver adjutting the flide, until the edge of it and the 

 black line coincide with both edges of the filament. An 

 4 K 2 horizontal 



