166 Notes on Small Motors. 



small industries and for scientific and domestic purposes is 

 undoubtedly one of the needs of the day. 



This need has for some years past been recognised by 

 mechanicians, and various machines have been devised, none 

 of which, however, have been generally adopted. Amongst 

 these may be mentioned diminutive steam engines, electro- 

 motors, hot-air engines, and gas engines. The first of these 

 are open to several serious objections. They are complex 

 and delicate, need much attention, and, worst of all, are 

 deficient in readiness, the process of getting up steam taking 

 considerable time. 



Electro-motors are simple in construction, and not easily 

 deranged. The battery is here the objectionable feature, being 

 a continued source of expense and trouble, and requiring the 

 use of materials the presence of which is, to say the least, by 

 no means desirable in the kitchen or larder. 



Hot-air engines compare favourably with the preceding in 

 most respects. They, however, are bulky and rather expen- 

 sive, and need a fire continually maintained beneath them. 

 The attention this fire requires and the waste heat radiated 

 from it are objectionable, especially in small workshops and 

 during warm weather. 



Gas engines of from one to ten horse-power are very much 

 in favour at present, and bid fair to supplant many of the 

 smaller steam engines, especially in positions when the 

 question of insurance is paramount. They are exceedingly 

 convenient, being always ready, and needing no attention 

 beyond lubrication. In first cost they are, however, very 

 expensive, and all that I have yet seen are far too large for 

 the purposes at present under consideration. 



There is one source of power usually present in important 

 towns which has yet to be noticed. In our street-mains we 

 have a large supply of water under a considerable pressure, 

 and capable of doing work to a corresponding extent ; and 

 if a suitable hydraulic motor can be found it is evident that 

 we have here a source of power which for readiness and 

 convenience can hardly be surpassed. This power has 

 already been generally adopted for the purpose of working 

 the bellows of large organs, but beyond this its application 

 has hitherto been very limited. 



To utilise the energy of the water is the question now 

 before us, and for this purpose several kinds of motor are 

 available. The ordinary piston and cylinder is very well 

 suited when a comparatively slow motion is needed, as in 



