C.—l.

at the outset that these instruments are intended to record the effect of very severe earthquakes which make themselves felt at a large distance from the seat of the disturbance. Some earthquakes have been known the waves generated by which have either travelled right round the world or twice through it, for they have been twice recorded at many stations, the second record being some hours after the first. It is earthquakes such as these that are of the greatest scientific interest, for the waves which are recorded by a seismograph, coming as they do through a portion of the earth's interior, bear on their surface the marks of the material through which they have travelled. While there is still much that is obscure, a certain amount has been already learned, and every record obtained gives fresh knowledge. A general description of the instrument may not be uninteresting. It is one of those designed by Professor Milne and known as a horizontal-pendulum seismograph. The principle of it is remarkably simple, and one with which every one is acquainted, being in effect an adaptation of the well-known swinging backward and forward of the boom of a yacht when that boom is not stopped from swinging by ropes or sail being set. As the yacht rolls the boom swings to and fro in response to its motions. If, then, the motions of the. end of the boom were watched, it would be possible to tell when waves were passing under the yacht. This is exactly what is done in the modern seismograph. An exceedingly delicately suspended aluminium boom has a hole in its free end, through which light from a lamp passes on to sensitive paper below. The paper is unrolled from a roll at a rate of about sixty millimetres of paper per hour. Motions of the end of the boom are accompanied of necessity by motions of the light spot on the sensitive paper, and thus any earth-waves which come are at once photographed. In this way forty-seven different disturbances have been recorded in Christchurch from the 23rd November till the 31st March, all of them being quite unfelt by persons either sitting or standing, and most of them originating at a great distance from these Islands. There are some forty of these seismographs scattered over the surface of the earth. The number of them is rapidly increasing. Those in our more immediate neighbourhood are at Wellington, Sydney, Melbourne, Perth, and Honolulu. There is also one just now erected somewhere in Victoria Land. It would be interesting and useful to have one in Norfolk Island. The custom in connection with the records is for details of the various shocks to be tabulated and sent round to the various seismological observatories. Any one can see on receipt of these circulars where any shock has originated from the times at which it has been recorded elsewhere. In accordance with this method the following circular has been sent round : — Reooeds of Milne Seismograph No. 16, at Christchubch. Latitude: 43° 31' 50" S. Longitude: 172° 38' 09" E. Time employed: llh. 30m. os. East of Greenwich. For the months of November, 1901, to March, 1902. No. 1, 2, .. . for each month. Time : N.Z.S.T., as stated above. P.T. = Preliminary tremors less than 2mra. complete amplitude; A.T. = After-tremors less than 2mm. cimplote amplitude; B.E. = Beginning and end of vibrations not loss than 2mm.; Amp. = Full amplitude in millimetres; B.P = Boom period. Midnight = oh. or 241).

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Maxima. No. n P.T. B. From To Amp. B. A.T. till. B.P. Remarks. 1 2 H. m. s. H. m. s. 23 25 13 0 0 13 48 0 N. H. m. s. H. m. s. 16 19 0 16 22 0 13 49 0 13 50 30 OVEMBEB, Min. 1-0 3-0 II. m. s. 13 52 0 H. ill. s. 14 30 0 Sees. 20 6 6 5 1 30 7 .. 1 42.10 9 2 13 0 2 30 20 15 10 40 0 10 57 0 27 31 10 20 0 10 56 27 31 18 1 17 31 20 56 35 20 57 24 Di JCEMKEK. 1 2 3 4 5 6 7 8 9 10 0 1 1 30 5 13 50 5 13 50 1 43 40 1 43 40 2 37 30 2 39 50 11 6 0 11 6 0 19 49 30 10 59 0 11 2 0 18 8 4 18 11 27 21 22 30 21 28 30 21 31 46 21 33 45 T 2-0 5-0 80 3-3 3-5 1-2 3-0 1-8 9-0 26-0 8-0 6-0 5 14 20 1 57 20 2 40 20 11 24 0 7 30 0 4 12 0 12 30 0 20 0 0 12 55 0 18 40 0 25 30 0 20 •20 20 15 17 18 18 18 11 6 35 21 51 0 1 2 3 4 5 6 7 8 9 10 11 12 1 3 9 18 15 17 19 21 22 22 24 25 17 14 22 17 39 40 J 17 46 1 2 24 5 2 37 15 11 37 40 10 32 0 18 6 30 12 16 50 11 29 44 11 52 18 21 52 17 10 11 30 17 53 0 21 26 32 11 18 35 11 19 30 11 21 30 11 25 28 11 39 50 'anuary. 10-2 2-0 2-2 5-2 0-8 0-8 0-7 1-8 0-8 O7 10 33 4 over 34 15-0 10-5 1-5 0-7 0-7 4-0 17 53 0 20 10 0 20 Very sharp tremor. Magnetograph much affected from 11.2 to 11.39. 11 29 40 10 9 30 18 0 10 18 48 30 11 19 16 21 43 0 10 2 18 17 47 0 10 24 45 10 40 0 12 17 0 11 27 0 18 12 0 12 42 0 12 9 0 22 5 30 10 22 0 17 58 15 18 18 18 IS 18 18 18 18 18 18 11 4 45 11 9 48 Very sharp tremor. The largest " shock" recorded to this date, but not felt personally. 16 0 40 17 4 0 18 56 0 1 53 15 12 19 7 15 0 0 16 13 0) 17 14 0) 13a 13b 14 15 26 2G 28 31 16 6 35 17 6 0 17 11 0 18 38 0 2 31 30 2 33 0 18 18 18 2 20 0 2 31 10 3 30 0