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tees, to send the boys on board of his vessels, and to leave the old men and the women to their fate. The painful task of delivering up the whole to the Prefect maritime, and to the Conseil de Préfecture, devolved on Van Swinden. This he did with an elaborate speech in the French language, in which he pointed out, in the strongest terms, the impolicy, the injustice, and the iniquity of this tyrannical act. Those who knew how matters were managed at that time, trembled at this piece of boldness, and every one expected to see Mr. Van Swinden transported to Paris. But the attention of the rulers of that period was soon strongly engaged elsewhere; and it was Van Swinden's good fortune to witness and celebrate the restoration of an institution which he so much valued. One of the first acts of the present King of the Netherlands was, to re-establish the school of navigation, and to restore to its trustees such property as had been saved from the French.

The following is a list of the principal works of Mr. Van Swinden :

Dissertatio de Attractione, 1766.

De Causis Errorum in Rebus Philosophicis, 1767.
Cogitationes de Variis Philosophiae Capitibus, 1767.
De Philosophia Newtoniana, 1779.

De Hypothesibus Physicis, quomodo sint e mente Newtoni intelligendae, 1785.

Tentamen Theoriae Mathematicae de Phaenomenis Magneticis. Lugd. Bat. 1772, 4to.

Observations sur le froid rigoureux de Janvier, 1776. Amst. 1777, 8vo. Recherches sur les aiguilles aimantées et leur variations. Mémoires Présentés à l'Académie des Sciences de Paris, t. 8.

Dissertation sur la Comparaison des Thermomètres, 1778, 8vo.
Observations Météorologiques faites à Franeker pendant l'année 1779.
Amst. 1780, 8vo.

Description of the Orrery made by Eise Eisinga in Friesland. Franeker,
1780, 8vo. (Dutch.) A new edition of this work is in the press.
Recueil de Mémoires sur l'Analogie de l'électricité et du Magnét
La Haye, 3 vol. 8vo. 1784.

Description du Planétaire de M. Adams, 1786. Plano.
Positiones Physicae, vol. i. and vol. ii. part i. Harderovic. 178
A Treatise on Finding the Longitude by Lunar Observations.
edition appeared in 1787, and the 6th in 1819. (In Dutch.)
A Treatise on the Use of Hadley's Octant and Sextant, 1788,
Dutch.)

Explanation of the Nautical Almanack, 1789, 8vo. Dutch.
Elements of Geometry, 1790, 8vo. The last edition appeared

Report on the Census of Amsterdam, folio, 1795.

On Weights and Measures. Amsterd. 1802, 2 vol. 8vo.

Lectures on Van Laun's Planetarium, Tellurium, and Lunarium. Amsterd. 1803, 8vo.

Besides these works, many papers drawn up by Mr. Van Swinden are printed in the Transactions of those Societies and Academies to which he belonged. In those of the Royal Institute of the Netherlands, there is one in the first volume, on the laws of atmospherical pressure, deduced from observations at Zwanenburg in Holland. In the third volume of the same collection, there is a paper in which Mr. Van Swinden maintains the rights of Huygens, as inventor of the pendulum: of this a translation has been given in Dr. Brewster's Journal.

We may still expect some publication on the invention of the telescope, and that of spectacles, by the same author. Some part of the correspondence of Van Swinden and Sennebier has been lately published in the Bibliothèque Universelle, tom. 24, December 1823.

UTRECHT, June, 1824.

ART. II.-Observations on the Pyro-Electricity of Minerals. By DAVID BREWSTER, LL.D. F.R.S. Lond. and Sec. R.S. Edin.

THE brilliant discoveries of Professor Oersted respecting the magnetical effects of electricity, and the highly important ones of Dr. Seebeck, relative to the thermo-electricity of certain metals, have attached a great degree of interest to the kindred subject of the pyro-electricity of minerals. In so far as we know, however, this circumstance does not seem to have drawn to the last of these classes of phenomena the attention of those eminent philosophers who have so successfully investigated the first; and we are not aware that any later observations have been made on the production of electricity by heat, than those which have been published by the Abbé Haüy.

The name of the philosopher who first observed that the Tourmaline was rendered electrical by the simple application of heat, has not been recorded; but there can be little doubt

that Lemery was the first author who mentions the circumstance. * M. Epinus of St. Petersburg, was the first per son who studied with ardour and success the phenomena which it presented. The experiments of this acute philosopher were published in the Memoirs of the Academy of Berlin for 1756, under the title of De quibusdam experimentis electricis notabilioribus. The examination of the subject was continued by Mr. Benjamin Wilson, Dr. Priestley, and Mr. Canton, who discovered the same property in the Brazilian topaz; but it was reserved for the Abbé Haüy to analyse the phenomena of the Tourmaline with the sagacity and patience of a philosopher, to add several new minerals to the short list of pyro-electrical ones, and to detect several interesting relations which had escaped the penetration of those who preceded him in the inquiry. The following is the list of pyro-electrical minerals, as given by Haüy, with the names of those who first noticed their pyro-electrical property.

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The principal phenomena of pyro-electricity, as observed in these minerals by the Abbé Haüy and preceding writers may be stated as follows:

1. When a prismatic crystal of tourmaline is exposed to an increasing heat, one of its extremities will exhibit vitreous, and the other resinous electricity, as may be easily seen by its action on an electrified needle, and by its power of attracting and repelling light bodies.

2. At a certain degree of heat, the tourmaline will no longer give indications of electricity; but in cooling it again the electricity will reappear, and when its temperature has been reduced to near 32° of Fahrenheit, the electricity again disappears; but upon the application of a greater degree of cold it reappears with opposite characters, the end of the tourmaline which had formerly exhibited resinous electricity, now exhibiting vitreous electricity. †

• Mem. Acad. Par. 1719.

+ This curious fact, announced some years ago as new by the Abbé Haüy, scems to have been discovered by Canton. See Edinburgh Encyclopædia, Article ELECTRICITY, vol. viii. p. 458.

3. In most of the crystals which become electrical by heat, the distribution of the electricity resembles the distribution of the magnetic influence in a bar of magnetised steel. The intensity of the pyro-electricity is a maximum at the two poles or extremities of the crystal, and gradually diminishes from these points to the central or neutral point equidistant from both, where it disappears.

4. In the Boracite, the pyro-electricity is distributed in á different manner. The primitive form of this mineral is cubical, and each of the four axes joining its solid angles has at its opposite extremities a vitreous and a resinous pole. If the crystal is made to revolve round any of its axes, the vitreous and resinous poles of the other axes will succeed each other alternately. The maximum intensity is very near the extre mity of each axis, and the intensity diminishes rapidly in re ceding from these points.

5. Haüy observed that the Electric Calamine was electrical at the ordinary temperature of the atmosphere, and exhibited the inversion of poles which he found in the tourmaline.

6. In studying the phenomena of pyro-electricity, Haüy remarked the curious fact, that while in the great mass of crystals the corresponding summits are similar in the number and disposition of their faces, while in pyro-electrical crystals there is a deviation from this symmetry. In the tourmaline, for example, the vitreous electricity resides in the summit with six faces, while the resinous electricity resides in the opposite summit with three faces. Hence it is supposed by Haüy, that the two fluids had exerted upon the laws of crystallization opposite influences, which had left their impress upon their crystalline form.

From this brief and general sketch of the labours of Haüy and others in this curious branch of physics, I shall now proceed tó give an account of the experiments which I made several years ago on the same subject, and of the results to which they lead. These experiments were made in the years 1817 and 1818; but the publication of them was delayed, in the hope that I should find leisure to extend them to large and well-formed crystals of the various bodies of the mineral kingdom. Having no prospect of accomplishing this task, I commit the subject into the hands of those who have more leisure, and would

recommend it as a fertile source of discovery to any young and active natural philosopher, who may have access to a good cabinet of minerals.

1. On the existence of Pyro-electricity in various Minerals.

In order to determine the existence of pyro-electricity in minerals where it had little intensity, I employed the thin internal membrane of the Arundo Phragmites, which was cut with a sharp instrument into the smallest pieces. These minute fragments were well dried, and the pyro-electricity of any mineral was determined by its power of lifting one or more of these light bodies, after the mineral had been exposed to heat. I used also a delicate needle of brass, the pivot of which moved upon a highly polished cap of garnet, and which was affected by very slight degrees of electricity.

In this way I determined the pyro-electricity of the following minerals:

Scolezite.*

Mesolite.*

Greenland Mesotype.

Calcareous Spar.
Beryl Yellow.

Sulphate of Barytes.
Sulphate of Strontites.
Carbonate of Lead.
Diopside.

Fluor Spar, red and blue.

Diamond.
Yellow Orpiment.
Analcime.

Amethyst.

Quartz Dauphiny.
Idocrase.

Mellite?

Sulphur Native.
Garnet.

Dichroite.

In examining the electricity of the tourmaline, I found that it could be shown in a very satisfactory manner, by means of a thin slice taken from any part of the prism. The experiment is most advantageously performed, when the slice has its surfaces perpendicular to the axis of the prism. When such a slice is placed upon a plate of glass, and the glass heated to the temperature of boiling water, the slice will adhere to the glass so firmly, that even when the glass is above the tourmaline, the latter will adhere to it for six or eight hours. In this way, slices of a very considerable breadth and thickness are capable of supporting their own weight.

It is probable, that the Mesotype of Hauy was one or other of these two minerals.

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