NECESSITY. 



NKKIM.E 



013 



1789. and conUioing 1000 additional nebulic. In 1802, he communi- 

 cated a third catalogue of nebula), containing 500 new objects. On 

 this lart occasion he dirtributea the various objects of the stellar regions 

 into twelve distinct rlnam. 



I. Itnlalfd iturt, such as Arcturus, Capella. Sirius, *c. 



II. Binary itart, or in other words, systems of two stars revolving ill 

 each ease about their common centre of gravity. 



III. Tiii le a*d .\fullijile itar*. 



IV. Clmtrrim/ nUtctiuai and the Ifilhj Way. Henchcl was of 

 opinion that in many park of the heavens the stars afford indications 

 of collecting together and forming distinct clusters from the effect of 

 their mutual attraction. He supposes that the Milky Way in under- 

 going a process of disruption from this cause. 



i-oHi>t of tlart. This consisted of aggregrations of stars whiob 

 did not exhibit any regularity of outline, nor condensation in any part 

 of their structure indicative of their forming separate systems. 



VI. dtiitrrt ofilan. These were objects of a round form, present- 

 ing in all cases a gradual condensation towards the centre. 



VII. .V. '/<*. These were supposed to be objects consisting in 

 reality of aggregate collections of stare. 



VIII. S>>llar xibultr.- These were imagined by Herscliel to be clusters 

 of stars situate at such immense dUtauces as to put on the aspect of 

 merely luminous points with burs. 



IX. Milky nebuloiily. This class consisted partly of aggregate 

 collections of stars which were nebulous only in appearance, and 

 partly of objects of a purely nebulous substance, like the nebula of 

 Orion. 



X. \eiiiloiuitari. These were stars surrounded by a nebulous 

 atmosphere. 



XI. Planetary nebultr. This class consisted of nebula: of a perfectly 

 round form, exhibiting a resemblance to the planetary bodies of the 

 solar system, only they shone by a very pale light. 



XII. Planttary ntbulre irith centra. The aspect exhibited by these 

 objects suggested the idea of a gradual condensation of the nebula into 

 a single luminous point. 



In 1811, Herschel communicated to the Royal Society a paper, in 

 which he explained his views of the transformation of nebulae into 

 stars. He endeavoured to prove that the nebulous substance, which 

 bis observations indicated to be extensively diffused throughout the 

 sidereal universe, had a tendency to form into distinct aggregations of 

 matter, in consequence of the mutual attraction of its particles, and 

 that the resulting mass in each case by a process of gradual conden- 

 sation finally acquired the consistency of a solid body. More recent 

 observations of nebula? have not served to confirm this bold hypothesis. 



In 1833, the younger Herschel communicated to the Royal Society a 

 payer, containing the results of a re-observation of the nebukc of the 

 northern hemisphere. These results are embodied in a catalogue con- 

 taining 2306 nebula; and clusters, of which about 500 were discovered 

 by himself. In 1828, Mr. Dunlop communicated to the Roynl 

 Society a catalogue of 629 nebula: and clusters observed in the 

 southern hemisphere ; and in 1847, the younger Herschel published 

 the results of his astronomical observations at the Cape of Qood 

 Hope which, besides various other objects of importance, contained 

 a catalogue of 1708 nebukc and clusters observed in the southern 



The most recent contribution to nebular astronomy is due to Lord 

 Rosne, who in 1820 communicated to the Royal Society a pa]*T. con- 

 taining the results of observations made by him, rim-fly with his 

 celebrated six foot reflector. One of the most remarkable facts dis- 

 closed by these observations consist* in the spiral arrangement of 

 several of the objects. It appears also from them, tli.it many nrliul.i- 

 which had been previously considered as irresolvible objects, consist 

 of agglomerations of stars, and the conclusion naturally suggested by 

 such observations is, that all nebulic are in reality nothing more than 

 aggregate macin of stars, which merely require telescopes of adequate 

 power to reveal their true structure. 



NKCKSSITY. [FBEE WH.I..] 



NECRO'SIS (from ngpii, " dead,") is the term applied particularly 

 to mortification or death of bone. Its general causes and the mode of 

 reparation are the same as those of mortification generally. [MoitTi- 

 XICATIOX ; INFLAMMATION ; BONE.] 



I > 1 . K M A N I ' F ACTURE. This branch of industry is supposed 

 to have originated in Spain, from the circumstance of the name 

 >>ini'A titedlr* being originally used in England, although the art was 

 brought here from Germany. Needles were first made in England 

 about the yew 1965, by Elias Crowse or Krauso, a German, who settled 

 in London ; or, a* others say, by a Spanish negro, who refused to reveal 

 the secrete of his art. The manufacture was lost to England for 

 nearly a century, but recovered about 1650, by Christopher Greening, 

 who settle I at Long Crrndon in lUiclcinguamMiire. The reputation 

 longenj'.yrd !;. II7,,/. rA;>e/ needles point* out the particular locality 

 in London where the manufacture was once carried on. At the present 

 time, the Urgent numbers of needles are made at Redditch in Worces- 

 tenhire, at Hathenage in Derbyshire, and in and new Itirmingham. 



The manufacturing processes are as follows : The steel is procured 

 from the Sheffield or Itirmingham wire-drawers, in coils of 121b. or 

 14 Ib of wire. The umul sizes of sewing needles vary from A to ^ of 

 an inch, and the wire is selected of corresponding thickness. The wire i 



cut into lengths equal to two needles ; and these lengths, being placed 

 together in a bundle, are brought to a glowing heat, and bound toge- 

 ther by means of iron rings from three to seven inches in diameter, 

 placed at each end of the bundle. This bundle is then placed on a 

 cast-iron table, and rolled to and fro upon it, under the pressure of a 

 flat bar of iron, by which means the wires are made perfectly straight. 

 Several of these wires are then taken by the grinder, and together are 

 pointed on a small dry grindstone. This process requires considerable 

 dexterity for its proper accomplishment, as each wire must be so h, M 

 by the grinder as to revolve in contact with the grindstone. It is this 

 dry grinding which makes the trade of a needle-grinder so injurious to 

 health, through the inhaling of the small particles of steel which are 

 thrown off during the operation. A preservative against this evil h*s 

 been provided : this consists of a mask of magnetic wire-gauze, worn so 

 as to protect the mouth: the particles of metal, being attracted by 

 this means, are prevented from passing into the lungs. It is but 

 seldom however that the grinders can be induced to wear these masks. 

 Needle-grinding in a well-paid but destructive employment ; some men 

 can grind 10,000 in an hour. 



When the pointing (at both ends) is finished, the holes or eyes are 

 perforated. This operation (on the hand method) is usually performed 

 by females. The tools employed are, a small anvil fixed on the work- 

 bench, a hammer, a finely-pointed and well-tempered steel punch, a 

 pair of plyers, a file, and a block of lead. The woman makes an inden- 

 tation on one side by means of the punch and hammer ; the needle L-, 

 then taken from the anvil, and being placed with the indented M If 

 downwards on the block of lead, the perforation is completed by 

 striking with the punch and hammer on the opposite side of the needle. 

 Holding then the needle in the plyers, the head is somewhat bent, and 

 with the file the guttering is performed, which is the forming of the 

 channel that may be seen on each side where the perforation is made. 

 The head is then smoothed by ]<assing the file over it. Needles to 

 which the name drilled-eyed is applied are perforated in the manner 

 here described, but the additional process is used of smoothing the eye 

 by means of a drill after it is perforated. In this hand method, the 

 wire is cut into two before the perforating, and the end of each piece 

 is slightly flattened with a hammer before the punch and drill are 

 employed. 



Machines, however, at first used for large needles, are now generally 

 used for all sizes. The wires, each about three inches long if to form 

 needles known as No. R, arc subjected to a stamping machine, in which 

 a weight of 30 Ibs. is brought down to stamp the gutter on each side 

 of the needle, and to make an indentation partly through the wire ; 

 this is done at the rate of 4000 wires in an hour. A tana hand press, 

 worked by boys, then drives each indentation right through the wire, 

 thus making perforations for the eyes of two needles. In fy. 1, lib is 



Fig. 1. Piercing Needles. 



the double needle, resting on the anvil a. held in its place by d, and 

 pierced by e. The wires are then " spitted ;" that is, two lino wires are 

 made to pass through the two eyea of several dozens of them, to hold 

 them while a man files off the burr left by the stamping. The work- 

 man then bends and works the comb of wires to and fro between his 

 hands, until he breaks each wire into two, leaving an eye or perforation 

 to each half. Fig. 3 shows five different stages of the needle, up 

 to the point where the wir.' is just about to be severed into two 

 and magnified representations of the last three of those stages. The 

 filer and two spittera prepare 4000 needles in an hour. 



These operations being performed when the steel wires are in a soft 

 state, the wires become more or less bent, and must be straightened, 

 which is done by rolling them on one plate of metal by a hin-ill. i 

 dexterously handled ; thin is called mfl-ttraiglitening. The needles aro 

 tlii-n placed, many thousands together, in a kind of crucible. Mini 

 covered over with ashes ; after which they arc put into a close furnace 



