6 Dr. Mac CuUoch on Mineralogkal Hammers. 



It is plain that, with a soHd of this form, any deviation from the 

 most favourable line of impulse which is likely to happen, will 

 have but little effect in diminishing the force of the blow; and that 

 the whole momentum will be concentrated on one point. From 

 the shortness of the blade, or the small distance of the face from 

 the axis of the handle, the missing of a blow by the sliding of 

 the hammer on an oblique surface, and its consequent attempt to 

 turn round, communicates no strain to the hand. 



The weight of such a hammer need not be very great, nor is any 

 advantage, indeed, to be gained by increasing it beyond a certain 

 point, proportioned to the strength of the arm which is to use it ; 

 as, in such cases, the power of the impulse is diminished. A few 

 trials will convince any one that, with "this construction, a given 

 weight will produce as great an effect as the double, or even much 

 more, would do in a flat or broad faced hammer. It is not conve- 

 nient, however, that it should be less than two pounds, and it 

 need not exceed four. With hammers of these weights so con- 

 structed, almost every object of the mineralogist can be ob- 

 tained. A weight of three pounds forms a convenient general 

 size for most purposes ; and, to facilitate the construction, I 

 may add that, allowing the usual general size for the eye, or 

 hole, the relative diameters of 3^ inches by 2, of 3| by 2i-, and 

 of 4 by 2|, will, in the form here represented, give pretty nearly 

 the weights of two, three, and four pounds, respectively. 



The artist intrusted with the making of these hammers must 



