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
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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
