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Rh ted with the usual solutions of sulphate of copper and sulphuric acid. A highly-polished steel plate was placed in a porcelain soup-plate, and a "filtered solution of acetate of lead poured upon it. A piece of card-board, out of which the required figures had been previously cut with a sharp knife, was then placed upon a steel-plate. Over the card, and resting on it, there was fixed a ring of wood, a quarter of an inch thick, and the inner circumference of which was of the same size as the figure. A convex copper-plate vras made so that its outer edge might rest on the inner part of the wooden ring ; and its centre placed near, but not in actual contact with the card-board. Connexion was then made by the positive electrode of the battery with the steel-plate ; the negative being placed in the centre of the copper convex plate. The figure was generally obtained in from 15 to 35 seconds. If a concave, instead of a convex plate be used, the same colours are obtained as in the former experiment, but in an inverse order.

" Geographical position of the principal points of the Triangula- tions of the Californias and of the Mexican coasts of the Pacific, with the heights of the principal points of that part of the Cordille- ras." By the Comte Vincent Piccolomini ; in a letter addressed to Sir John F. W. Herschel, Bart., V.P.R.S. Communicated by Sir John Herschel.

Hauteurs des principaux points des Cordilleres, des cotes de V Ocean Pacifique du Mexique, et de la haute et basse Californie.

Elevation en pieds frangais sur le ni- veau de la mer pacifique.

Volcano di Orizaba 18728

Volcano di Popocatepetl.. 17812

Volcano di Tztlacihuatl... 15698

Riofrio 10948

Real del Monte 10570

Eloro 8995

Tlalpuhahua 8435

Ameia 8247

Naupalucan 8194

LasVigas 7918

Perote 7911

Ozmnba (Etat de Puebla) 7874

Tepeyahualco 7702

Ozumba (Etat de Mexico) 7620

S. Rosa 7565

Lagunas de Chalco 7510

Mexico 7450

Tepeaca 7444

Huebuetaca 7121

Puebla 7078

Tula 6613

Tlacotepec 6479

Zacualpan 6181

Elevation en pieds frangais sur le ni- veau de la mer pacifique.

Tasco 5971

Temascaltepec 5760

Guernavaia 5447

Tcbuacan 5398

Xantetelco 5030

Cuicatlan 5028

Oajaca 5024

Cuautla 4587

Talapa 4542

Acayucan 4485

Coscomatepec 4451

Huatusco 4424

Talostoc 4421

Lautepec 4019

Orizaba (%dUe) 3998

Real de Christo 3851

Huaitla 3336

Cordova 2769

Dominguillo 2274

ViUale 1578

Petapa 617

Tehuantepec (Ocean Pacifique.) 132