AMERICAN Horological Journal. VOL. I. NEW YORK, JULY, 1869. NO. 1. CONTENTS. ASTRONOMY IN ITS RELATIONS TO HOROLOGY, 5 WATCH AND CHRONOMETER JEWELLING, 11 HINTS ON CLOCKS AND CLOCK MAKING, 15 NOTICES OF NEW TOOLS, 17 GREENWICH OBSERVATORY, 17 PINIONS, 20 NEW THREE-PIN ESCAPEMENT, 23 ENGLISH OPINION OF AMERICAN WATCH MANUFACTURE, 23 CORRESPONDENCE, 24 ECLIPSE OF THE SUN, 25 DIAMOND CUTTING, 25 ALLOYS OF ALUMINUM WITH COPPER, 25 EQUATION OF TIME TABLE, 28 ⁂ _Address all communications for_ HOROLOGICAL JOURNAL _to_ G. B. MILLER, _P. O. Box 6715, New York City. Publication Office 229 Broadway._ Astronomy in its Relations to Horology. NUMBER ONE. However accurate an instrument for the mensuration of time may be, it would be of little use for close observation unless we have some standard by which to test its performance. We look to Astronomy to furnish us with this desideratum, nor do we look in vain. The mean sidereal day, measured by the time elapsed between any two consecutive transits of any star at the same meridian, and the mean sidereal year--which is the time included between two consecutive returns of the sun to the same star--are immutable units with which all great periods of time are compared; the oscillations of an isochronous pendulum affording us a means of correctly dividing the intermediate space into hours and days.