by the use of .steam power was taxed “because it is á matter of common- knowledge that, the hydroelectric comr panies use steam power to supplement water power in the production Of their current, and also because current produced by steam power is the great competing factor .'on the market with -current produced by water power.” 52 F. (2d) p. 519. This classification cannot be regarded as arbitrary. Nor can it be .doubted that, the State- was entitled, in devising its. fiscal system, to recognize the distinction between hydroelectric companies generating electric current for sale-to;the public and industrial plants which develop power for their own use and that of their employees. The principles involved have' been so -recently restated by this Court that-elaboration is unnecessary. Heisler v. Thomas Colliery Co., 260. U. S. 245; Ohio Oil Co. v. Conway, 281 U. S. 146; State Board of Tax Commissioners v. Jackson, 283 U. S. 527.
(2) The. separate complaint of the Lexington Water •Power Company is that it. is generating current át a water power- plant, .on the Saluda river, which was constructed and- is operated pursuant to a license granted by the Federal Power Commission under the Federal Water Power Act (16 U. S. C.,- c. 12) and hence that the tax is an “ excise, license or privilege tax ” upon a Federal •agency.
It is apparent, however, that the complainant in generating and selling power is not acting as an agent for the . Government. It acts with the Government’s permission, and .while it may be said to have received a privilege from thé Government, it is not a privilege to be exercised on behalf of the Government. The tax is not upon the exertion of, and.cannot be said to burden, any governmental function. Fox Film Corp. v. Doyal, 286 U. S. 123, 130. The tax is not laid upon thé license granted by the Federal. Watér'Power Commission , but upon the production and sale of power which. the company generates at its own