vi Preface 



time- cost is not so important as that of the perfection of the 

 product ; while some are inferior, in consequence of the limi- 

 tations of skill, tools, etc. It would not be expected, e.g., for 

 a teacher to weld the two pieces of a broken steel pin or 

 shaft, though possibly this would make the best job. He has 

 to be content with half-lapping, drilling, and riveting, which 

 are processes entirely at his command. Similarly, it is not 

 necessary from a carpenter's point of view to include the 

 tongue in the back bracket of the Hare's apparatus on page 19; 

 but this is inserted (i) as an exercise, (2) in order that 

 the ordinary shaky construction of the amateur may be 

 stiffened extra strength of design being made to take the 

 place of skill in construction. 



The craftsman will doubtless find humour in some of the 

 suggestions put forward herein, but it should be remembered 

 that we are first of all teachers, and that we must use skill 

 in craftiness in order to overcome our lack of the craftsman's 

 skill. These are methods that will serve our purpose, and 

 they are within our resources. 



The professional apparatus maker will have no cause for 

 alarm, rather will he be gladly rid of the many repairs that 

 fall to his lot from time to time, and are so unsatisfactory. 

 The teacher will henceforth pull down his " repairs," in order 

 to learn the principles of construction, and buy a new appa- 

 ratus ! He will no longer blame the professional repairer, for 

 having seen the hopelessness of some of his own efforts, he 

 will respect more fully the new apparatus, and protect it 

 from damage with greater assiduity; and, knowing more of 

 the principles of construction, will be the less likely to put his 

 apparatus to undue strain. 



