As such, it calls attention to the fact that the amount of insurance claims met, and of interest receipts, _are limits_ which the corresponding expenses cannot exceed, certainly for a series of years together, without making the _expense_ more than the _advantage_ of the business. To keep this fact in view, _as a preventive of extravagance_, is not the least valuable service the new mode may render. It may be seen that there are eight cases in the table, in which the ratio of insurance expense points to expenses exceeding the insurance claims met in the same time, yet the reader need not hasten to conclude that the same companies will permanently show similar ratios, or have no good reasons to give for the ones which now appear. I may remark, however, that it is an evidence of the scientific mode in which the figures are presented, that it facilitates such explanations as are pertinent of any of the ratios. For instance, some of the ratios are undoubtedly affected by the fact that the claims for the year of the company in question have been exceptionally high or low, or that the company (being of recent organization perhaps) has just incurred exceptional expense to increase its business, the advantage of which will appear later, etc. But I leave to the companies themselves to show to what extent such circumstances have affected their ratios; except that, in regard to the several net rates of interest earned, it is proper to say that in all cases in which they considerably exceed the average of 5.42 per cent. it will be found, by referring to the details of interest receipts reported to the Commissioner, that the excess is owing to the fact of exceptional profits by the sale of stocks, or recovery on investments previously reckoned as loss. WALTER C. WRIGHT. Medford, Mass., Sept., 1884. * * * * * A catalogue containing brief notices of many important scientific papers heretofore published in the SUPPLEMENT, may be had gratis at this office. * * * * * THE SCIENTIFIC AMERICAN SUPPLEMENT. PUBLISHED WEEKLY. Terms of Subscription, $5 a Year. Sent by mail, postage prepaid, to subscribers in any part of the United States or Canada. Six dollars a year, sent, prepaid, to any foreign country. All the back numbers of THE SUPPLEMENT, from the commencement, January 1, 1876, can be had. Price, 10 cents each. All the back volumes of THE SUPPLEMENT can likewise be supplied. Two volumes are issued yearly. Price of each volume, $2.50, stitched in paper, or $3.50, bound in stiff covers. COMBINED RATES--One copy of SCIENTIFIC AMERICAN and one copy of SCIENTIFIC AMERICAN SUPPLEMENT, one year, postpaid, $7.00. A liberal discount to booksellers, news agents, and canvassers. MUNN & CO., PUBLISHERS, 361 BROADWAY, NEW YORK, N.Y. * * * * * PATENTS.