21. The Government may make rules- (a) for the specification, verification, correction and replacement of the Standard Test Apparatus; (b) prescribing fees for the inspection of the Standard Test Apparatus; (c) regulating the procedure in comparing a test apparatus with the Standard Test Apparatus; (d) prescribing the form of certificate to be given in respect of a test apparatus so compared, and the period for which such certificates shall be valid; (e) prescribing the form of the register of such certificates; (f) prescribing fees for comparing a test apparatus with the Standard Test Apparatus; (g) regulation the procedure of testing officers in carrying out tests of petroleum, providing for the averaging of results where several samples of the same petroleum are tested, and prescribing the variations from standard temperatures which may be allowed; (h) prescribing the form of certificates of tests of petroleum and the fees which may be charged therefor; (i) providing where the results of the testing of samples raise a doubt as to the uniformity of the quality of the petroleum in any lot under test, for the division of the lot into sub-lots, and for the selection and testing of samples of each sub-lot and for the averaging of results in accordance with the results of tests of those samples; (j) prescribing fees for re-tests under section 20 and providing for their refund where the original test was erroneous; and (k) generally, regulating the procedure of all officers performing duties connected with the testing of petroleum and providing for any matter incidental to such testing.