MESSRS. EDITORS.—For many years our law-makers have endeavored, by various en- . actments, to secure accurate weight to the j purchasers of coal and other articles. A bill is now before our Legislature, the provisions of which will compel the coal-dealers of this city to weigh every load of coal at the door of the consumer. This will involve the necessity of portable scales, or scales attached to every coal cart. The retail coal trade of this city alone is estimated at half a million of tuns per annum. Were only the nominal tax. of five cents per tun exacted from the above business, for the use of a suitable self-weighing cart, it would secure to the fortunate inventor the comfortable sum of $25,000 per annum. Should the bill before our Legislature be adopted, it will, doubtless, be but initiative to laws of a like character in other States having such large coal-consuming cities as New York, Boston, Philadelphia, &c. Who will be the first, among your host of ingenious readers, to furnish us with an accurate, simple, and durable self-weighing cart ? A COAL DEALER. Philadelphia, Pa., February, 1858. [By referring to No. 7, Vol. XII, of the SCIENTIFIC AMERICAN, our correspondent will find " an accurate, simple, and durable self-weighing coal cart," patented by one of his own townsmen.—EDS.