At present no uniform method is observed by the consumers of gas for keeping a check upon the inspectors who examine the meters monthly, and take down, for the accounts of the gas companies, the amounts consumed. The monthly inspectors may make false entries, and the consumers of gas thereby suffer. To afford a check against such a result, Mr. A. N. Brewer, of this city, has designed a tabulated index to hang up beside each meter for the inspector to enter the amount registered on the index of the meter, and th quantity consumed during the month. These entries will enable the consumer to examine the meter for himself, and to keep a check upon the inspector and the bills of the gas company. It is a very useful improvement, and it is surprising that something of the kind has not come into general use long before this. The Senate has passed a bill giving $20,000 to Edward N. Kent, in full compensation for the use in the United States Mints of his apparatus to separate gold and silver, and other precious metals. It was illustrated on page ; 81, Vol. XI., SCIENTIFIC AMERICAN.