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GEORGE IIOGGAN ON A 



as it does between the saw guides (which have been utilised as 

 guides for it also) keeps the free edge always close up to the edge 

 of the razor and immoveable in that position ; the tray itself is 

 easily moved backwards and forwards by the fingers, but the re- 

 quisite heavy pressure is brought to bear upon it by a screw (g), 

 fixed in a cross beam (h), which slides on to the top of the frame- 

 work when required. 



In cutting hard sections the bottom and moveable side, as well 

 as the cross beam, may be removed and replaced in less than a 

 minute, so as to impede in no way the working of the machine. 



Now suppose we wish to cut a section of some soft material, it 

 seldom happens that it fits exactly the cavity or box of the machine, 

 and consequently some matrix is necessary to hold it firm, and for 

 that purpose I have found nothing better than a piece of fresh hard 

 carrot. 



A cube of this vegetable is roughly shaped to the size of the 

 box of the machine, then cut into two halves ; a cavity roughly 

 adapted to the size of the article to be cut is formed between the 

 halves, and these, with the article between them, having been 

 placed in the machine, are firmly compressed by screwing down the 

 movable side upon them when it is ready, and firmly fixed for 

 making sections ; only one caution being necessary, namely, never 

 to cut as far as the brass table, or the razor will be blunted at once. 

 Therefore, under all circumstances, some carrot must intervene be- 

 tween the material to be cut and the brass table. 



Now for a word as to the kind of knife best adapted for cutting 

 sections. I myself always use a razor for that purpose, either 

 with the edge quite straight or the lower surface quite flat, so that 

 the section may be of equal thickness throughout ; these precau- 

 tions are highly necessary. In all cases the upper surface of the 

 razor or knife is ground as hollow as possible (as it usually is), and 

 it also ought to be as broad as possible, so that it may serve 

 as a sort of reservoir to contain the liquid used in lubricating the 

 razor. Upon the surface of this liquid all delicate sections are 

 floated off while they are being cut, to prevent them from breaking 

 up, collapsing, or being otherwise destroyed. I use various liquids 

 for this purpose, such as glycerine, methylated spirit, turpentine, or 

 oil of cloves, water, &c. ; but the two best, that I have not hitherto 

 made public, are : water, to which a little caustic soda or potash has 

 been added, till it feels like oil, for some substances ; and the 



