From September 26, 1882, to September 1, 1883, night and day uninterruptedly, a watch was kept, in which the officers took part, so that the observations might be regularly made and recorded. Every four hours a series of direct magnetic and meteorological observations was made, from hour to hour meteorological notes were taken, the rise and fall of the sea recorded, and these were frequently multiplied by observations every quarter of an hour; the longitude and latitude were exactly determined, a number of additions to the catalogue of the fixed stars for the southern heavens made, and numerous specimens in natural history collected. The apparatus employed by the expedition for the registration of the magnetic elements was devised by M. Mascart, by which the variations of the three elements are inscribed upon a sheet of paper covered with gelatine bromide, inclination, vertical and horizontal components, with a certainty which is shown by the 330 diurnal curves brought back from the Cape. The register proper is composed of a clock and a photographic frame which descends its entire length in twenty-four hours, thus causing the sensitized paper to pass behind a horizontal window upon which falls the light reflected by the mirrors of the magnetic instruments. One of those mirrors is fixed, and gives a line of reference; the other is attached to the magnetic bar, whose slightest movements it reproduces upon the sensitized paper. The moments when direct observations were taken were carefully recorded. The magnetic _pavilion_ was made of wood and copper, placed at about fifty-three feet from the dwellings or camp, near the sea, against a wooded hill which shaded it completely; the interior was covered with felt upon all its sides, in order to avoid as much as possible the varying temperatures. The diurnal amplitude of the declination increased uniformly from the time of their arrival in September up to December, when it obtained its maximum of 7'40", then diminished to June, when it is no more than 2'20"; from this it increased up to the day of departure. The maximum declination takes place toward 1 P.M., the minimum at 8:50 A.M. The night maxima and minima are not clearly shown except in the southern winter. The mean diurnal curve brings into prominence the constant diminution of the declination and the much greater importance of the perturbations during the summer months. These means, combined with the 300 absolute determinations, give 4' as the annual change of the declination. M. Mascart's apparatus proved to be wonderfully useful in recording the rapid and slight perturbations of the magnet. Comparisons between the magnetic and atmospheric perturbations gave no result. There was, however, little stormy weather and no auroral displays. This latter phenomenon, according to the English missionaries, is rarely observed in Tierra del Fuego.