CONVENIENCE OF MANIPULATION. 97 



that they are often intended for a great variety of tests, 

 both as to the sizes of specimens, and to the kind of 

 stress imposed. If it were not for the fact that a testing 

 machine, especially a large one, is an expensive thing to 

 buy, the ideal arrangement for a testing laboratory would 

 be to have a different machine for every kind of test. 



51. Ease of Access to the Specimen. It is always 

 desirable that the specimen being tested shall be accessible 

 for inspection and the taking of observations during the 

 test. Where the specimens are of ordinary length, there 

 is not much difference in this respect betAveen horizontal 

 and vertical machines. The Wicksteed four-pillar machine 

 is perhaps the one best adapted for obtaining a view of the 

 specimen on all sides, although for some purposes the pillars 

 are somewhat of a hindrance when fixing in' the specimen. 



Where the specimen is long, there is no doubt that the 

 horizontal possesses many advantages over the vertical type 

 of machine. It is a great convenience to have the whole 

 of the specimen at a uniform and convenient height from 

 the ground, say about three or four feet. The difficulty 

 of testing long specimens in a vertical machine has been 

 partially overcome, in one machine built by Messrs. Buckton, 

 by providing a movable platform which can be raised or 

 lowered to any required height ; on this platform the 

 operator stands when taking his observations. 



It is sometimes objected that compression specimens 

 tested horizontally tend to sag downwards and always fail 

 by bending in this way. But results would appear to show 

 this to be a fallacy, so far as specimens of the usual 

 dimensions are concerned. 



52. Convenience of flanipulation. When a speci- 

 men which is to be tested has been placed in the holding 

 shackles and more will be said about these later the 

 application of the pressure and the measurement of the 

 load should be capable of easy and convenient regulation 

 by the operator. The best arrangement is to have, within 

 easy reach of the operator at the same time, two handles 

 one to control the supply of water under pressure into 

 the straining cylinder, and the other to vary the position 

 of the lever weight. If these two are at different parts of 

 the machine, or if the water is pumped in by hand as it is 

 wanted, an additional assistant will be required. A large 

 single poise-weight, like that used in the Buckton machine, 

 has the advantage in simplicity and in many other ways, 

 but in point of ease of manipulation it falls behind 

 machines of greater leverage and smaller weights. 



H2 



