For more complete information on this subject, your readers may be referred to a small work entitled “New Varieties of Coins and Bullion, &c., by J. R. Eckfeldt and W. E. Du Bois, Assayers of the Mint. 1850,” and to a pamphlet entitled “Guide to the Value of California Gold, by Geo. W. Edelman, U. S. Mint, 1850.” Very respectfully, your obedient servant, GEO. F. DUNNING. Rev. Daniel B. Woods, Philadelphia. P.S.--The following rules for making calculations of weight and value may not be unacceptable to the readers of your book. 1. _To convert Pounds Avoirdupois to Ounces Troy._--From the avoirdupois weight, expressed in pounds and decimals of a pound, subtract one eighth. Divide the sum thus obtained by ·06, and the quotient will be the Troy weight in ounces and decimals. 2. _To convert Ounces Troy to Pounds Avoirdupois._--Multiply the Troy weight in ounces and decimals by ·06. To this product add its seventh, and you have the avoirdupois weight in pounds and decimals. 3. _To find the Standard Weight of Gold or Silver, the gross weight and fineness being given._--Multiply the gross weight, in Troy ounces and decimals, by the fineness in thousandths, and divide the sum by 900. The quotient will be the standard weight in ounces and decimals. 4. _To find the Value of Gold and Silver._--GOLD. Multiply the standard weight, in Troy ounces and decimals, by 800, and divide the product by 43. The quotient is the value in dollars and cents. SILVER. To the standard weight, in Troy ounces and decimals, add its one eleventh part, and eight tenths of one eleventh. The sum will be the value in dollars and cents. 5. _To convert the fineness expressed in Carats into Thousandths._--Multiply the carats by 41⅔. The product is the equivalent fineness in thousandths. Since the completion of my work, I have received from Col. J. J. Abert, of Washington, the Report of P. T. Tyson, Esq., presented to the Senate of the United States by the Secretary of War. Although it is too late to avail myself of the valuable information contained in this report from one who has made a thorough and scientific reconnoissance of the mineral and vegetable wealth, the climate and agriculture of California, I am induced to present a few extracts, which refer more immediately to the mines. It was a source of much gratification to find the views and statements I have given so fully corroborated by this report. It will be noticed that the averages of the daily profits of the miners arrived at by Mr. Tyson, as the result of careful observation, differs but a trifle from the averages given in this volume. In his article upon the gold regions, he writes: