NAUTICAL ASTRONOMICAL INSTRUMENTS, &c.

[Class X.

signal almost instantaneous in duration can be recorded,by the momentary interruption of the circuit.

The practicability of this method of recording observa-tions is placed beyond a doubt by experience in America ,and from the results there obtained, this method ■wouldappear to be more accurate than that usually adopted bythe combination of the eye and ear. The question yetremains to be determined, ■whether there be a closer con-nection between the nerves of the eye and the ear, orbetween the nerves of the eye and the linger, and thisquestion can be settled only by experiments.

The Council Medal has been awarded to Messrs. Bond.

Nautical Instruments.

Exhibitors of nautical instruments are few in number,and, with the exception of those exhibited by Ericsson(United States , No. 146, pp. 1442-1446% and those bySt. John (United States , No. 95, p. 1439), display butlittle novelty, and no decided improvements.

Tlie sea-lead and the several other instruments exhibitedby Mr. Ericsson, reflect high credit upon him: they areoriginal in their design, well adapted for their work, anduseful.

Nautical Astronomical Instruments.

Simms (No. 741, pp. 475*, 476*), exhibits aTroughton’sreflecting-eircle, 10 inches in diameter, with three equi-distant verniers reading to 20" of arc, having an achro-matic telescope witli eye-pieces magnifying 8 times and15 times, supported upon a counterpoise stand, withmotions for placing the instrument in a vertical, oblique,or horizontal plane.

This instrument was invented by the late EdwardTroughton, and was designed as an improvement on thereflecting-circle, previously in very general use. With it,a cross observation gives six readings upon the circle,which is perhaps as high a degree of accuracy as is attain-able by any instrument held in the hand, and such anobservation is obtained with much less labour than oneclaiming equal confidence upon the ordinary repeating-circle.*

Mr. Simms also exhibits a Troughton’s sextant (p.477*), fixed upon a counterpoise stand; this instrumentwas contrived for the purpose of combining strength withlightness, and consists of two thin frames of brass, unitedby pillars. This form was suggested to the inventor by ;his having observed, that with one of the large open-framed sextants, a contact of the sun’s limbs made withtlie telescope directed upwards was but apparent, a largespace occasionally intervening when the telescope wasdirected downwards into an artificial horizon.

This form of sextant has not only maintained itsground, but would appear by those exhibited to be fastverging on general adoption. It is usually made of8 inches radius, and is divided to 10" of arc.

A Prize Medal was recommended by the Committeeupon Sextants for these instruments of Mr. Simms.

Barrett (No. 349, p. 449) exhibits several sextants,one of which is furnished with a magnifier, prepared forreading without shadow by night; the instruments are forthe most part of an ordinary character, nevertheless Hon-ourable Mention was awarded to Mr. Barrett.

Crichton (No. 452, p. 462,) exhibits many sextants,some of a very ordinary kind; there are two, however,numbered 2251 and 2252, which are well made, but thedivisions on the vernier and on the limb do not agree inany of them. In connection with drawing instruments,&c., a Prize Medal was voted to Mr. Crichton.

Mrs. Janet Taylor (No. 350, p. 449,) exhibits a sex-tant intended rather for show than use. Other exhibitorsof sextants are Elliott and Sons (No. 322, pp. 444-446),Watkins and Hill (No. 659, p. 438), and Dixey (No.271, p. 466*).

Molteni and Siegler (France , No. 649, p. 1209, ex-hibit sextants and reflecting circles, pretty good in all

* For a full description of this instrument, see il Pearson’sAstronomy,” and “ Encyclopaedia Metropolitans,” vol. i.,p. 63S.

respects, the divisions excepted. The Jury awarded theseinstruments Honourable Mention.

Vedy (France , 719, p. 1213,) has exhibited a reflectingBorda’s circle divided to 20', and read by means of ver-niers to 20". A reflecting circle made after the improve-ments of Captain Richards, by means of which very largeangles may be measured.

A sextant read by verniers to 20"; another divided to10% and read by a vernier to 10"; a third and fourth,reading to 15"; a fifth, whose reading is to 30"; and asixth, which reads to one minute. M. Vedy also exhibitsan artificial horizon. These instruments are well made,and a Prize Medal was awarded to M. Vedy.

Buron (France , No. 443, p. 1199) has exhibited varioussextants and octants in ebony and brass, furnished witlicoloured glasses to the number of five or seven, and withboth direct and inverting telescopes. The sextants aredivided to 10% and subdivided by verniers to 10'% Thesize and the construction of these instruments are in everyrespect like those made in England. Their divisions aregood, and their price is low.

Beaulieu (Belgium) exhibits a sextant of 7*5 inches.The graduations are on silver to 10", sexagesimal,with every means for verification. The body of the in-strument is in one piece, and is very solid: a secondsextant of the same size, divided, Sec as the preceding;another sextant of 6*3 inches radius, furnished with thesame accessories as the preceding, and reads to 15" sexa-gesimal; a fourth sextant of 4*3 inches radius, divided to20" sexagesimal, a fifth sextant of 2*8 inches radius,divided on silver to sexagesimal minutes; a sixth sextantof ebony 9*4 inches radius, divided upon ivory to 30"sexagesimal; also an octant in ebony of 10*6 inchesradius, divided on ivory to sexagesimal minutes, and twoartificial horizons. The sextants are solid and well made,and the work of ail is good.

A Prize Medal was awarded to M. Beaulieu.

Oertling, A. (Prussia, (1) No. 87, p. 1053,) exhibitssextants whose divisions on the limb are faint, hut good;the verniers are such that it is difficult to judge of thereading to 10" in the larger, and to 16" in the smallersextants.

Imperial Ijorsk Works (Russia , No. 169, p. 1372,)exhibits two of the largest sextants in tlie Exhibition,being 10 inches radius. These are sound and well made,and reflect credit upon tlie artists.

Asiie (No. 194, p. 431) exhibits an instrument for de-termining the course which a ship must steer to sail on agreat circle. That the instrument will do its work ismore than probable; but whether it has any advantageover the published tables for the same purpose is morethan doubtful.

Various Nautical Instruments.

Ericsson (United States, No. 146, pp. 1442-1446,) liasexhibited a sea-lead. This instrument, which is designedfor making soundings at sea, independently of tlie lengthof the lead line, and without the necessity of rounding thevessel to the wind, is a modification of an instrument for-merly constructed in conjunction with Mr. Ogden, ofLiverpool.

The instrument consists of two large tubes; a chamberis placed immediately behind, and connected by means ofa small bent orifice to the upper extremity of one of them.The top of the second is connected by a similar orifice toa third small tube suspended in the centre of the chamber.A stop-cock is placed at the lower end of the glass tubesfor the purpose of cutting off communication, if ne-cessary.

The lead being bent to the line is lowered into the sea,as it sinks, the water enters the chamber, and graduallyrising in it and in the tube suspended within, causes anincreased pressure upon the air, which is driven throughthe orifices into the glass tubes. The tube which is con-nected with that in the chamber will be entirely filledwith the air thus forced into it from the suspended tube,the water will consequently rise, and its reading may beobserved upon the graduated scale with which the instru-ment is furnished for that purpose.

The contents of the chamber being much greater than