THE object that the writer has mainly in view in presenting this paper is to draw the attention of those connected with the technical side of the industry to the unsatisfactory and by no means up-to-date methods employed in estimating the tin contents of an ore. At the same time, what is regarded from the writer's personal experience, as "a satisfactory and reliable method is explained in detail. It is a curious fact that for the last 25 years tin-assay methods have made little or no advance, while those now in general use in connection with copper and lead ores can scarcely be compared with those then obtaining, so greatly have they been improved upon. Though it is not altogether expected that the method herein advocated will at once meet with general approval, the writer hopes the resultant discussion may bring out points that have hitherto escaped detection.