January 21, 1887.] 



SCIENCE, 



57 



pipe, which pipe enters the room at a height of about 

 ten feet, and, passing downward, ends in a faucet over 

 a zinc-lined sink, the sink being connected by a pipe 

 with the ground. The ball of fire was about an inch 

 and a half in diameter, of a semi-transparent bluish 

 color, giving a feeble light, which first appeared at 

 the top of the pipe, and rolled down it at a nearly 

 uniform velocity of six or eight feet per second, and, 

 upon reaching the faucet, fell into the sink with a 

 report abotit as loud as the discharge of a gun-cap. 

 We at once examined the sink, but found no trace 

 of any thing. But, as we stood watching the pipe, the 

 same phenomenon was twice repeated, making three 

 discharges in the course of ten minutes. 



This occurring, as it did, five years and a half ago, 

 I am unable to give as accurate an account as I 

 might wish. There were twelve or fifteen persons in 

 the room at the time, some of whom I have since 

 seen, and all agree. In regard to the location, it was 

 in the Sunset Hill house on Siigar Hill, in the White 

 Mountains, about seventeen hundred feet above the 

 sea. The pipe which supplies water to the house 

 comes from a spring on the mountain-side, and, pass- 

 ing up through the wall, leads to a reservoir on the 

 roof of the kitchen. 



The pipe on which the globular lightning was seen 

 is a branch of this main pipe. On its way to the 

 upper story — starting from a height of about ten 

 feet, it comes out of the wall, and passes downward 

 at an angle of about 30** with the vertical, ending in 

 a brass faucet over the sink. The pipe was of 

 wrought iron, covered inside and out with a coating 

 of coal-tar to prevent rusting. 



The phenomena described occurred during a heavy 

 thunder-storm, and, so far, as I can learn, nothing of 

 the kind had ever happened there before, nor has it 

 even been repeated. N. C. Waedwell. 



Hartford, Jan. 10. 



The genesis of the diamond. 



In an interesting communication under this title, 

 Pz-of. H. Carvill Lewis gives in No. 193 of Science 

 an apparently satisfactory theory of the structure and 

 origin of the diamond-bearing necks of South Africa 

 and of the genesis of the gem in that region. The 

 discovery of undecomposed peridotite as the original 

 form of the puzzling blue ground confirms the suspi- 

 cion long entertained by my friend, Prof. Henri 

 Goraix, and myself, that very slight analogies, if any, 

 exist between the South African and Brazilian dia- 

 mond-fields, in the latter of which we have, as we 

 think, traced the diamond to its original matrix. 

 Communications on the subject will be found in the 

 American journal of science for February and July, 

 1882, by myself, and in papers by Professor Goraix 

 in the Comptes rendus de Vacadimie des sciences and 

 Bulletin de la SociiU giologique de France of 1884. 



The main points of these papers may be briefly sum- 

 marized as follows. The diamond region about the 

 city of Diamantina, in the province of Minas-Geraes 

 (the oldest and best-known diamond-field of Brazil), 

 consists geologically of very ancient and profoundly 

 disturbed metamorphosed strata, which may be di- 

 vided into three groups : 1", wholly crystalline 

 rocks, gneiss, mica-schists, etc. ; 2", less perfectly 

 crystalline rocks, unctuous schists, quartzites (itacol- 

 umites), iron ores (itabirites), and limestones ; and, 

 3°, quartzites. The first two groups form the nucleus 

 of the mountainous diamond-bearing region, No. 2 



greatly predominating over No. 1. No. 3, which in 

 hand specimens (and often in the field as well) can 

 only with difficulty be distinguished from the 

 quartzite of group 2, with which it has up to the 

 present been very generally confounded, lies in 

 undulating folds over the upturned edges of Nos. 

 1 and 2, and at times passes to a conglomerate 

 including fragments of both the older groups. 

 The geological age of these groups is undeter- 

 mined, but the newest of them can scarcely be 

 younger than the Silurian, and, if not older, belongs 

 more probably to the earlier than to the later part 

 of that age. The eruptive rocks thus far recognized 

 in the diamond district are granites, diabases, gab- 

 bros, and serpentinous rocks, which very probably 

 were originally peridotites. It should be remarked, 

 however, that the latter are apparently far less 

 abundant than in the region farther south in the 

 same mountain-range, in which diamonds are only 

 found rarely, or, over large areas, not at all. 



The greater part of the diamond-washing, being in 

 river-alluviums or in gravel- deposits on the uplands, 

 gives no clew as to which of the three groups or of 

 the associated eruptions may have furnished the 

 gems. A few of the upland gravel-deposits are evi- 

 dently decomposed but undisturbed conglomerates 

 belonging to group 3. The famous Grao Mogol 

 locality described by Helmreichen, Claussen, and 

 Heusser and Clary, where diamonds are found em- 

 bedded in a hard quartzite with a conglomeritic 

 character, belongs also, in my opinion, to this group ; 

 the diamond entering, like the other elements, as a 

 rolled pebble. Professor Goraix, however, who has 

 had the advantage of a personal examination of the lo- 

 cality, refers the diamantiferous rock to the quartzites 

 of group 2, and admits the possibility of the genesis of 

 thegemm siiu, though he does not insist very strongly 

 on this point. The difficulty I have often experi- 

 enced in distinguishing the quartzites of the two 

 groups one from the other, even when they are in 

 juxtaposition in the same section (as I believe Profes- 

 sor Goraix admits them to be at Grao Mogol), leads 

 me to the apparent presumptuousness of maintaining 

 my opinion against that of so acute and conscien- 

 tious an observer. 



At a single locality, Sao Joao da Chapada, the 

 miners have penetrated deeply the decomposed but un- 

 disturbed schists of group 2, extracting the diamond 

 from a decomposed vein-rock from which Professor 

 Goraix took out, with his own hands and with all 

 possible precaution against error, several of the pre- 

 cious stones, after I had expressed to him the opinion 

 that it was the veritable matrix of the diamond. 

 Three veins of somewhat different character have 

 been recognized. One is of quartz with plates of 

 specular iron, to which the diamantiferous barso 

 (clay) adheres. This last is an earthy mass rich in 

 iron, which gives, on washing, an abundance of 

 microscopic tourmaline. This last circumstance, 

 with the abundance of iron, suggests a comparison 

 with the peculiar auriferous veins of quartz, pyrites, 

 and tourmaline of the vicinity of Ouro Preto in 

 the same geological horizon, and in very similar 

 conditions. The other veins are without quartz, 

 and consist of a lithomarge-like clay charged 

 with oxides of iron and manganese, which, as 

 Professor Goraix states, bear a strong resemblance, 

 both in composition and geological occurrence, to 

 the topaz and euclase bearing viens of the vicinity 

 of Ouro Preto. These veins are coincident with the 



