128 OBSERVATIONS ON THE CONSTRUCTION AND USE 



SECT. I. General Observations on the Construction and Uses of the Imple- 

 ments used in Horticulture. 



Implements may be considered with reference to the mechanical prin- 

 ciples on which they act, the materials of which they are constructed, their 

 preservation and their repairs. 



387. All tools and instruments, considered with reference to the mechanical 

 principles on which they act, may be reduced to the lever and the wedge ; 

 the latter serving as the penetrating, separating or cutting, and sometimes 

 the carrying part ; and the former, as the medium through which, by motion, 

 force is communicated to the latter. All the different kinds of spades, 

 shovels, and forks have their wedges in the same plane as the levers ; all 

 the different kinds of picks, hoes, and rakes have their wedges fixed at 

 right angles to the levers. The blades of knives and saws are no less 

 wedges than the blades of spades or rakes, only their actions are somewhat 

 more complex ; every tooth of the saw acting as a wedge, and the sharp 

 edge of a knife consisting of a series of teeth so small as not to be visible 

 to the naked eye, but in reality separating a branch by being drawn across 

 it, on exactly the same principle as the saw. The series of combinations 

 which constitute machines, when analysed, may be reduced to levers, 

 fulcrums, and inclined planes ; and utensils depend partly on mechanical 

 construction, and partly on chemical cohesion. It is only by understanding 

 the principles on which an implement is constructed that that part can be 

 discovered where it is most vulnerable when used, or most liable to decay 

 from age. In all tools and instruments the vulnerable point is the fulcrum 

 of the lever, or the point where the handle is connected with the blade or 

 head. Another reason why failure generally takes place in that part is, that 

 the handle is there generally pierced with a nail or rivet, which necessarily 

 weakens the wood by breaking off or separating a number of the fibres. In 

 general, the power or efficiency of any tool or instrument, supposing it to 

 be properly constructed, is as its weight taken in connexion with the motion 

 which is given to it by the operator. Hence strong-made implements of 

 every kind are to be preferred to light ones ; and this preference will be found 

 to be given by all good workmen. 



388. In the construction of implements, the levers or handles are for the 

 most part made of wood, and the wedges or operating parts of iron or steel. 

 The wood in most general use for handles in Britain is ash ; and next to the 

 ash, oak : but for lighter tools, such as the hoe, rake, the scraper, besom, 

 &c., pine or fir deal is sufficient. Handles to implements are of four kinds : 

 first, cylindrical and smooth from one extremity to the other, as in the hoe, 

 rake, &c. ; second, cylindrical, or nearly so, but dilated at one or at both 

 extremities, as in the pick, hatchet, &c., such handles being called helves ; 

 third, cylindrical and smooth, but with a grasping piece at one end, as in 

 the spade, shovel, &c. ; and fourth, angular or rough throughout, as in the 

 pruning-knife, hammer, hedgebill, &c. The reasons for these forms of 

 handles are to be found in the manner of using the implements : one hand 

 of the operator is run rapidly along cylindrical handles, as in the hoe and 

 rake ; in the dilated handles, one hand slides along between two extremities 

 till it reaches the dilated part of the head, which wedges firmly into the 

 hand ; and, this dilated part being in the direction of the operating part of 

 the tool, adds considerably to its strength. This is the case in the pick, and 



