“ Both treat the question as affecting the solution of other contentions. There has been no ruling on the point by the Supreme Court of the state. We think the tax in its essence is what the act calls it-an occupation tax. It is not laid on the land containing the ore, nor on the ore after removal, but on the business of mining the ore, which consists in severing it from its natural bed and bringing it to the surface where it can become an article of commerce and be utilized in the industrial arts. Mining is a well-recognized business, wherein capital and labor are extensively employed. ”

“ Every person engaged in the business of mining or producing iron ore or other ores in this state shall pay to the state of Minnesota an occupation tax equal to 6 per cent. of the valuation of all ores mined or produced, which said tax shall be in addition to all other taxes provided for by law, said tax to be due and payable from such person on May 1 of the year next succeeding the calendar year covered by the report thereupon to be filed as hereinafter provided.↑ In 1921, out of a total output of 18,167,370 tons, the amount sold and used within the state was 261,622 tons. ”

“ One is that contractors who strip off the overburden of soil, gravel, etc., in open pit mines, other contractors who load the ore in such mines into cars, and still others, usually four in a group, who take ore out of underground mines, are not included. But none of these are engaged in mining on their own account. Instead, they are working for those who are so engaged. However important their service, they are not principals in the business, but employees ”

“ It may select those who are engaged in one class of business and exclude others, if all similarly situated are brought within the class and all members of the class are dealt with according to uniform rules. ”

“ The contentions made under the equal protection provision of the Fourteenth Amendment and under the state constitutional provision that 'taxes shall be uniform upon the same class of subjects' present a question or classification and have been argued together. ”