The amount of havoc in our wheatfields created yearly by them is enormous. Their forwardness and activity have driven all other birds from where they have settled, so that the hairy caterpillars, which sparrows do not eat and which used to be extensively consumed by other birds, are now greatly on the increase, probably the only creatures, at present, enjoying the domestication of the sparrow in this country.... I have also to remark that the sparrows here betray much less pugnacity than in Europe.--E.M., M.D. * * * * * It is stated in the _Chemical Review_ that recent analyses of the water from the _Holy Well_ at Mecca, which is so eagerly drunk by pilgrims, show this water to be sewage, about ten times stronger than average London sewage. * * * * * HOW TO ESTABLISH A TRUE MERIDIAN. In looking over the excellent article of Professor S. M. Haupt, in the SCIENTIFIC AMERICAN SUPPLEMENT, No. 360, on the subject of finding the meridian, I discovered that one important step is not given, which, might prove an embarrassment to a new beginner. In the fourth paragraph, in the third column of page 5,748, he says: "Having now found the altitude, correct it for refraction, ... and the result will be the latitude." It will be observed that this result is only the true altitude of the star. The _latitude_ is found by further increasing or diminishing this altitude by the polar distance of the star. This paper will be of great value to engineers and surveyors, for the elementary works on surveying have not treated the subject clearly. H. C. PEARSONS, C.E. Ferrysburg, Mich. * * * * * 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, 261 BROADWAY, NEW YORK, N. Y. * * * * * PATENTS. In connection with the SCIENTIFIC AMERICAN, Messrs. MUNN & Co. are Solicitors of American and Foreign Patents, have had 35 years' experience, and now have the largest establishment in the world. Patents are obtained on the best terms.