. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 530 A UNIVERSAL METEOROGRAPH, ing wire to the positive pole of a battery, the negative pole'of which is connected in the same way with the minute hand, the current will then pass so long as the gold point rests in contact with the divided circle, but when the point meets one of the indexes the current will be inter- rupted for an instant by the interposition of the ebouite tip, but will be restored so soon as the point is freed from that ob
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 530 A UNIVERSAL METEOROGRAPH, ing wire to the positive pole of a battery, the negative pole'of which is connected in the same way with the minute hand, the current will then pass so long as the gold point rests in contact with the divided circle, but when the point meets one of the indexes the current will be inter- rupted for an instant by the interposition of the ebouite tip, but will be restored so soon as the point is freed from that obstacle. When the minute hand has traversed the entire circle—that is to say, nfter an hour's time—the current will have been momentarily interrupted (in the example we have chosen) six times. These interruptions may now be made use of at the central observatory, which communicates by means of a telegraph wire with the outlying observatory, to record the indications of the instruments on a cylinder covered with a sheet of pa- per, rotated by clock work once an hour, the rotation of which is therefore isochro- nous with that of the minute hand at the outlying station. The isochronism of the two movements is the condition on which the accuracy of the meteorograph depends; in order to judge if it is fulfilled, little ebonite plates cecare fixed on the divided circle. We will see, later, how these plates give the desired in formation in regard to the working of the clock at the detached ob- servatory. On the spindle of the registering cylin- der (Fig. V) is cut a screw-thread which runs in the nut p, so that at each revolu- tion the cylinder descends a little—for example, a millimetre (Jg- inch.) Beside the cylinder an electro-magnet, A, is placed, which attracts a piece of soft iron, b b, hinged at d, to which is attached a pencil, steel point, or diamond, pressed against the cylinder by a spring. While the current is closed the pencil is kept away from the cylinder, but at e
Size: 943px × 2650px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorsmithsonianinstitutio, bookcentury1800, bookdecade1840
