185 (53)
5. The mould is immediately opened and the briquette removed and placed flat on a sheet of glass, which is then reared on a shelf at an angle of 45 degrees and supported.
6. During the process of drying the briquette slides down the glass till it is stopped by the shelf, allowing a slight settlement of the material on itself to prevent cracking due to shrinkage.
7. At the expiration of 14 days the briquette is carefully pared down to the exact
size in the centre of 1" x 1".
8. It is then placed carefully in the clips and the strain applied.
9. In No. 1 machine as used at the Public Works Departinent the strain is applied by means of a sliding weight which is caused to travel along a lever by means of a wheel and cord. As this machine is designed for the testing of cement, which requires a breaking strain of from about 50 lbs. up to as much as 800 lbs. per square inch, it is extremely doubtful whether it can be relied upon to register such small strains as 1 to 5 lbs. with accuracy.
10. No. 2 machine at the Public Works Department is on the same principle, but the weight is applied at end of lever by means of shot poured into a bucket, this also is designed for cement testing and the same objection holds good; but owing to the more gentle method of applying the weight and better construction of the machine, the Building Authority prefers results obtained on this to those of No. 1.
11. Briquettes are broken by Messrs. LEIGH & ORANGE in the following manner :-
The upper clip is rigidly fastened to a beam, the lower clip to which is attached an empty kerosene tin is placed in position and water slowly poured into the tin till the briquette breaks, the whole suspended weight is then weighed.
12. No. 3 machiue designed by the Building Authority and now in use is a more
compact and sightly arrangement on the principle described in No. 11, is no more accurate.
but