Section 12. On any such testing, if it appears to the officer or other person so testing that the petroleum from

12. On any such testing, if it appears to the officer or other person so testing that the petroleum from which such sample has been taken is or is not dangerous petroleum, such officer or other person may certify such fact, and the certificate so given shall be receivable as evidence in any proceedings which may be taken under this Act against the dealer in whose possession such petroleum was found, and shall, until the contrary is proved, be evidence of the fact stated therein; and a certified copy of such certificate shall be given gratis to the dealer at his request. Penalties. Penalty for illegal importation, &c., of petroleum.