In the summer of 1896 the Oxford Museum was enriched by a fine series of about eighty mineral specimens from a newly opened quarry at Haddam Neck in Connecticut, which were kindly presented by Mr. Ernest Schernikow of New York.

The species included in the series are green and pink tourmaline, albite, microcline, green and pink apatite, brown fluor, beryl, quartz, cookeite, lilac lepidolite, greenish-white muscovite, and a peculiar pink fibrous variety of the same mineral. To these must also be added, as occurring at the same place, green fluor, microlite, and columbite.

The locality is described as Haddam Neck, a village opposite to Haddam, on the other (eastern) bank of the Connecticut River, which is here about half a mile wide.

The validity of Haüy's great law of the rationality of intercepts — better known as the law of rational indices—or its equivalent, the law of homogeneity of arrangement of the ultimate particles in a crystalline structure, has as yet never been seriously called into question : nevertheless, in the crystals of the telluride of gold, calaverite, we find characters which are to all appearance at variance with this law. As far as the author is aware and can ascertain, no difficulty of a precisely similar kind has ever been encountered before. Certain substances do, indeed, display the so-called optical anomalies; but these are, as was first established by Mallard, in reality in strict accordance with the actual crystalline arrangement.

For this new mineral I propose the name baumhauerite in honour of Dr. H. Baumhauer, Professor of Mineralogy in the University of Freiburg, Switzerland, who has done so much to elucidate this complicated group of sulpharsenites of lead.

System: Oblique. a : b : c = 1.136817 : 1 : 0.947168; β = 82° 423/4.

These elements are calculated from the angles 100 : 101=50° 27′ 101:001 = 32° 153/4′ and 010 : 111̄ = 50° 33′ measured on crystal No. I.

The crystals closely resemble dufrenoysite and jordanite in appearance. They may be distinguished from dufrenoysite by the marked oblique development of the zone [100,001], and from jordanite by the absence of twin striations and by the colour of the streak. The edges in the pyramid zone and between planes in the zone [100,010] are more or less rounded.

The mineral described below was found by the present writer, in the year 1893, at Kodikanal on the Palni Hills, in the Madura District of the Madras Presidency. These hills, which rise at Kodikanal to a height of 7000 feet above the sea, form a range some thirty miles long in a WSW.-ENE. direction, with a breadth about half as great. They are composed of grey igneous rock, belonging to Mr. T. H. Holland's ‘Charnockito’ series, the slight foliation being in a direction coincident with that of the range, while the dip is at high angles. The mountains are at present mostly clothed with grass only, the soil being highly Charged with peaty matter, and moderately fertile.

Historical Introduction.—As given in modern text-books, the holohedral-cubic silver haloids occurring as minerals include the following species: the pure chloride, chlorargyrite, AgCl. ; the pure bromide, bromargyrite, AgBr; the intermediate embolite, Ag(Cl,Br), containing chlorine and bromine in varying proportions ; and iodobromite, containing all three halogens in a definite ratio corresponding to the formula 2AgCl.2AgBr.AgI.

The terms hornsilver (used by Gesner as far back as 1565) and cerargyrite (Beudant, 1832) are usually taken as referring only to the pure chloride. As regards their signification, however, they are equally applicable to all of the above species, and in lack of chemical analyses were certainly so applied in the past. Thus Breithaupt, after the discovery of the bromide and chloro-bromide of silver by Berthier in 1841 and 1842, remarks that many of the specimens of ‘Hornerz’ in the Werner Museum having a greenish colour probably contained bromine.

The mineral kilbrickenite was analysed, described and named by Dr. James Apjohn in 1840. The specimens which he examined were sent to him by Mr. P. M. Taylor, who conducted the mining operations at the Kilbricken mine in County Clare, where the mineral was discovered. Apjohn's analysis showed the presence of lead, antimony and sulphur in proportions corresponding fairly closely with tbe formula 6PbS.Sb2S3. It was only in the preceding year that L. F. Svanberg had described a new mineral, geocronite, to which he assigned the formula 5PbS.(Sb, As)2S3. The announcement of this new mineral appears to have escaped Apjohn's notice, since geocronite is not included in the list of sulphantimonites of lead with which he concludes his paper.