60 
FIRST REPORT— 1831. 
Mr. Abraham exhibited another Magnetical Instrument, in¬ 
tended to guard the eyes of the grinders from the dispersion of 
fragments of steel, communicated several poles to the same 
magnetic bar, and detailed the method which he had found 
most effectual for communicating, combining, and increasing 
the magnetic influence. 
He then exhibited his simple process for demagnetizing the 
steel balance-wheels of watches. Having dipped a balance- 
wheel, previously rendered magnetical, into iron filings, and thus 
discovered the situation of its poles,—he presented to one of 
these, at the distance of an inch, the similar pole of a small 
magnet. The filings immediately fell from the wheel, and it 
was found to be perfectly demagnetized. (Mr. Abraham’s in¬ 
ventions having been presented to the Society of Arts, are de¬ 
scribed in their Transactions, Vol. XL. p. 135; Yol. XLIII. 
p. 48; Vol. XLIV. p. 19.) 
WEDNESDAY MORNING. 
Dr. Brewster communicated a paper, which was read by 
Mr. Robison, presenting a general view of the progress of the 
science of Mineralogy during the last thirty years, and of the 
principles of classification now adopted for minerals ; and sug¬ 
gesting the propriety of adding to the four systems of crystal¬ 
lization now employed by Mohs and other mineralogists (the 
Rhomboidal, Pyramidal, Prismatic, and Tessular systems,) a 
fifth, viz. the Composite system, as combining a series of cry¬ 
stalline structures not included under the other heads, and 
mostly discovered by the agency of polarized light. This new 
system of crystallization, the Author proposes to divide into 
two classes, the first of which embraces those minerals in which 
the physical properties of the individual crystals are not altered 
by the combination; and the second , those minerals in which 
the physical properties of the individual crystals are altered by 
the combination. These classes were again divided into dif¬ 
ferent orders, and the Composite minerals were enumerated, 
which the author proposed to place under each division. 
The following Essay by Dr. Henry, was then read by Mr. 
Phillips. 
An Estimate of the Philosophical Character of Dr. Priest¬ 
ley , hy William Henry , M.D ., F.R.S ., §c. tyc. 
The principal source of the materials of the following pages, 
is the work, in which the discoveries of Dr. Priestley were 
originally announced to the public. It consists of six volumes 
