1.50 



DRUG-GRINDING. 



KckhanU's 



rolling 



etonc. 



PLATE 

 ( ( XI.. 

 Fig. 6. 

 I _ 



is made pretty long, to permit the ston. to n-<- up, 

 when there i- a considerable thickness of matter be- 

 neath them, without raising the shaft. The Atones 

 ought to grind the drugs to powder, independently of 

 merely roUng over it, by a sort of rawing motion 

 which they II.IM- itjxm the Iwd. This i-. produced by 

 the -tones Al? being cylinders of i -le. breadth, 



and turning round on a small circle upon tlic bed stone: 

 Hence the edge of the stone which is nearest to the 

 centre of the sh:itt does not describe so large a '.rcle, 

 or paw through so great a space as the outside edge, 

 which is more distant from the centre ; but ns all part* 

 of the breadth of the runner move with the same velo- 

 city runnel its own axis, some parts must of course have 

 a sort of grinding motion upon the bed stone, the outer 

 parts of the edge of the runner moving upon the bed 

 slower than it would move by mere contact with its 

 surface, and the inner parts of the edge moving slower. 

 This circumstance very materially aids the operation of 

 the grinding, and by constantly disturbing the materi- 

 als, it prevents them from consolidating into a cake. 

 The rolling stones will levigate to an almost impalpable 

 powder, if their action is continued long enough, and 

 will reduce almost any substance, if the weight of the 

 ninners is proportioned to the hardnos of the material 

 they are to grind. All drug mills have several sets of 

 these stones, of different sixes ; and a great advantage in 

 the use of them is, that they are very readily cleaned 

 from afi remains of any drug. When it is required to 

 grind a different sort, it is done by first sweeping them 

 clean, and then grinding them for a few minutes on 

 dry bran, or saw-dust, which takes up every particle 

 from the stones. 



Fig. 6. is another kind of rolling stone, invented by 

 Mr F.ckhardt. In this the runner A is almost of the 

 shape of a bottle, and is placed upon an inclined axis 

 B, supported in a frame DEF, which revolves upon 

 two pivots, one at a, in the centre of the bed-stone H, 

 and the other at e, sustained by the framing of the null. 

 To the upper part of the revolving frame, the large 

 cog-wheel FF is fixed, to turn the machine round. The 

 bed stone H is hollowed, as shewn in the Figure, to 

 adapt it to the action of the runner. This machine is 

 well adapted for reducing drugs to an impalpable pow- 

 der, by a long continued action. The runner should 

 then be light, that it may take less power to work it. 



Fig. 4. represents a different method of levigating. AB 

 is a cast-iron pot, shaped like a cone, with a hemispherical 

 bottom. In this is placed an iron grinder 1), which is 

 rather conical, and has a spherical end, to fit the bot- 

 tom of AB. At the upper end of D, a heavy weight 

 E is fixed. The materials to be ground are thrown in- 

 to the vessel AB, in small quantities : then the grinder 

 being caused to revolve round in the pot, rolls succes- 

 sively over every part of the interior surface of the 

 cone, and grinds upon the drugs within it, a sufficient 

 pressure being occasioned by its own weight, aided by 

 that of the mass E. The motion is communicated by 

 m vertical spindle F, supported in framing G, so as to 

 be exactly in the axis of the cone AB. It is kept in 

 constant motion by a pinion, working in the great wheel 

 H of the mill. On the lower end of the spindle, an 

 arm .5 is fixed, and has at the extremity an eye to re- 

 ceive the end of the grinder ; therefore, when the .spin- 

 dle turn*, it moves the grinder round in its pot ; but 

 that it m.iy be allowed to accommodate itself to the 

 quantity of matter which it rolls over, the eye of 5 does 

 not fit the end of the grinder, but a collar a is fitted 

 upon a pivot, formed at the upper end thereof; and this 



is connected by two links, like a chain to the sides of 

 the eye, as shewn in 1 ig. .">. This machine will vcrv 

 effectually reduce drugs to an impalpable powd, 

 cause the powder is kept in constant agitation ; and 

 therefore, every lime the grinder rolls o\er it. new sur- 

 &CM are ground, mid no particle can i -cape. This agi- 

 tation is occasioned by the low er end of the grinder un- 

 dermining the powder, which has been caked up against 

 the opposite side of the cone, by the grinder rolling 

 it, and by breaking the cake it causes it to fall (low n, 

 as shewn in the Figure. The pot is surrounded by a 

 table I, to prevent any tiling being lost ; and thi 

 be extended to any si/e, to contain several machines, 

 which, being arranged in a circle, will all be actuated 

 by the same large cog-wheel I i. The tine sorts oi 

 are ground in machines on this principle. 



Fig. 2. is a machine used by Mr Raw 1 in son of Deri y. 

 to grind indigo, or other drugs, in a dry state. A, is a 

 mortar, formed of marble, and nearly hemispherical 

 within. The muller or grinder R, is lilu w i\e of marble, 

 and revolves within the other, being t'.irned by means 

 of a crank 1), funned on the spindle, which is support! -d 

 vertically in the frame E. The muller is shaped 

 thing like a pear, and has in the lower part a cleft, or 

 notch, which is of great use in keeping the materials in 

 constant motion, whilst they are ground between the. 

 surfaces of the muller and that of the mortar. The pres- 

 sure is regulated at pleasure, by the addition of weights 

 F, on the upper end of the spindle, in addition to the 

 weight of the muller. 



Fig. 8. is a method of grinding, which is equally 

 applicable for reducing dry powders, or for preparing 

 them in a semi-fluid state, as colours and some drugs 

 are prepared ; for there the great object is to produce a 

 thorough incorporation of the ingredients with the 

 fluid. A A is a circular iron vessel, the bottom of which 

 is adapted to receive three or four large cannon shot 

 BB. These are made to roll round within it, by the ac- 

 tion of arms a, which project from a vertical axis I); 

 for as this revolves, its arms push the cannon balls 

 round in the vessel A, and they roll over the drugs. 

 For dry grinding, the ends of the amis are made long 

 enough to reach down to the bottom of the vessel, i'.nd 

 thus rake up the powder immediately after the ball has 

 passed ; a circumstance which is essential for making 

 impalpable powders, because, when the substance 

 ground to a certain degree of fineness, the pressure will 

 otherwise consolidate the powder into a cakc.and prevent 

 its further reduction. The axis D may be put in motion 

 by wheel-work from the mill, or by a bevelled wheel d, 

 working in the teeth of a pinion e, which is situated 

 upon the horizontal axis /! This has a handle upon one 

 end of it, by means of which a boy turns it; and at the 

 other end is a fly wheel, to regulate the motion. The 

 framing is too evident to require any explanation. 



Fig. 7. is another machine, acting with cannon balls; 

 it consists of an iron vessel AA, of a circular figure, 

 having its interior surface cast with three semicircul-ir 

 channels, running all round it, for the reception of the 

 shot I! 111!. The vessel is mounted upon an axis I), 

 which is supported in framing EE, and by means of 

 a large cog wheel F, the whole is turned round with 

 the same motion as a barrel churn. This causes the 

 balls to roll within it, mid as the balls and the powder 

 will always occupy the bottom part, the powder is re- 

 duced as fine as possible, by the balls passing over it. 

 The powder constantly falls down from the upper part 

 of the vosel to the lower, and thus every part of the 

 mass is subjected to the action of the bulls. A graft 



nrn. 



Kig. i. 





Mat-hint 

 with can- 

 nun balls, 

 Kig. V. 



Anothrr 

 machine 

 with U1U. 



