Feb. tj, 1865.] 



KNOWLEDGE 



lo;; 



rods or thick sheets of metal. For copper, brass, or iron a 

 saw is necessary, but slcel should never be loiic/ied with a 

 saw. There are three forms of saws to bo used in working 

 metals. 



Ex. XIX. The first is the back-saw (Fig. '2), in which 

 the blade A 1>, about •"> in. long and 1 in. wiJo, is lixed in 

 the back, C D. The back is fastened into the handle, E, 

 the axis of which is in a line with the back. 



Ex. XX. The framesaw is shown in Fig. 3. To the 

 handle, E, is attached the frame, ABC. The saw (12 in. 



Fig. 3. 



long) is attached to the frame at B and C, and is tightened 

 by the nut, D. 



Ex. XXI. The fret-saw is used when cutting sharp 

 curves. A similar (but lighter) frame to that employed in 

 Ex. XX. is used, the narrow blades, which are made inter- 

 changeable, being suitable for cutting curves in material 

 which is not of a heavy nature. The size of the saw 

 depend.-! upon the kind of work to be performed. 



Ex. XXII In essay iug to saw a piece of copper or brass 

 (sheet or rod), place the metal in a vice, and cut the faces 

 with a frame- or back-saw. It is necessary that the young 

 worker should practise himself on this work, paying par- 

 ticular attention to the way in which he holds and works 

 his saw. He must keep it as nearly horizontal as possible 

 throughout the stroke, and should make a horizontal cut in 

 the metal. He must avoid making a cut which is, say, 

 half an inch deep at the extremities and only a quarter of 

 an inch in the middle. When the faces are all cut, the 

 piece of metal may, if the cuts are deep enough, be broken 

 into two parts, by fixing one end in a vice, and breaking the 

 parts asunder. If unable to break the metal, it should be 

 sawn a little deeper, and again tried until it does become 

 breakable. 



Ex. XXIII. To cut iron, the same general plan may be 

 adopted, using the frame-saw, with — in the case of wrouglil 

 iron — a liberal supply of oil or water, but omitting this 

 when cutting cast iron. 



Ex. XXIY. To cut steel, which, as already stated, must 

 not be attempted with the saw, cut all the sides with the edge 



Fig. 4. 



of either a half-round (Fig. 4), three-square (Fig. 5), or 

 crossing (Fig. G) rough file. Then snap off the part to be 

 removed in a strong vice. Should it happen that there is 

 no %'ice available of sufficient strength, place the line of 

 severance over a hole, not less than an inch in diameter, 

 in an iron plate, and strike it with the edge of a hammer, or 

 the piece of steel may be laid over two straight pieces of 

 iron and then broken between them by a smart blow from 

 a hammer. There is some little danger attending this 

 operation, as one portion of the steel being held, the other 

 will fly if the fracture is obtained. If, however, a .second 



party is not present, and the worker kei^ps hi.s face clear, 

 he need have no fear of any hurm being done. Somctimos 

 the process fail.-i, in which case tlio cut is insulllcit'ntly deep. 

 It should be deepened and the hanmiering repeated until 

 success is attained. 



ON TERMITES. 



By Surgeon-Geneual K F. Hutchinson, M.D. 



ri"^HE vulgar idea at home is that India is a prey to pests 

 X of all .sorts ; that you cannot go abroad without en- 

 countering a tiger or treading upon a serpent ; that you 

 cannot remain at home without meeting scorpions, cen- 

 tipedes, or spider.^, or having your clothes, books, and boxes 

 destroyed by moths, white ants, or borers ; your eatables 

 devoured by rats, and your drinkables detlled by musk 

 shrews. 



This idea is virtually an enormous growth of exagge- 

 ration sprouting from a germ of truth. 



I have resided thirty years in this country, and, at 

 various intervals, have encountered all these pests, but with 

 two exceptions, every one of them can be avoided with the 

 most ordinary care. Do what }0U will, you must, in some 

 r.iiapo or other, encounter the white ant, or wood-borer, 

 butb, enigmatically, most formidable instruments of destruc- 

 tion, and marvellous agents of renovation. The borers I 

 .shall dismiss, merely remarking that they are the familiar 

 death-ticks, larvre of various longicoru beetles, and that 

 their special function consists in restoiing humu.s to the 

 soil in the shape of impaljiable wood-dust ; while the func- 

 tion of white ants lies in subsoil ploughing on a marvellous 

 scale ; they bring up mud from the subsoil water-level, that 

 is from 8 — 15 — 20 ft. below the surface, and distribute it 

 over the land ; and, indirectly, they distribute humus from 

 the wood they feed on. 



Formicologists reject the white ant fiom the auty brother- 

 hood, because they s »y it is a neuropterous insect, while the 

 black aut is hymcnopterous; this is very much a distinction 

 without a difference, inasmuch as the white insects are ants 

 to all intents and jiurpose.s, but because they are blanched 

 from courting darkness rather than light, the black ants 

 regard them as lawful prey, and devour them ruthlessly 

 whenever they have the chance. And ]ierhaps, too, this 

 ho-tility is due to the acknowledged superiority of the 

 albino as a mechanical workman of the highest order. 



Here this humble insect is fucilc jirinceps over all orders 

 of creation. No elephant, with his strength and bulk, 

 could go through the patient and enormous labour of the 

 white ant, and what a terrible foe he would be to man- 

 kind it he possessed the indomitable energy of the termite 

 in all matters of destruction. Let me explain my meaning. 

 Come with me to this tree, and watch the open end of this 

 delicate mud-tunnel running up its side, and here five feet 

 from the ground. If you have a lens, so much the better. 

 Note the little fringe of antenme busily at work in 

 finding the proper spot for the little pellicles of rnud 

 which you can just see in the jaws of the upside- 

 down workers (all work upside-down while clinging 

 to the roof of their tunnel) ; that found, you see 

 the pellicle carefully deposited, and then .smoothed 

 into position. The process seems simple, but it really 

 means that each humble unit has brought its pellicle of 

 mud from the subsoil* water level, and that, in this 



* This level, of course, changes with the season; during the 

 rains it is comparatively superficial, sinks during the cold weather, 

 and is at its maximum at the end of the dry season, just before 

 the rains. 



