486 



NATURE 



[Sept. 1 8, 1879 



tion the indications given by alloyF, when under the influence of 

 the induced current, bear to their electric conductivities. 



The experiments on a comprehensive series of alloys proved 

 that, in the case of alloys of certain metals, the induced- 

 current curves closely resembled those representing electric con- 

 ductivity, but that in certain other cases the induced current 

 revealed differences that had hitherto escaped observation. As 

 an example, Mr. Roberts alluded to the curve of the copper-tin 

 alloys, in which there is a sudden break between the points 

 representing two alloys, which only vary by a single equivalent, 

 or by 6'4 per cent, of copper. These two alloys are widely dif- 

 ferent in colour, fracture, den!-ity, and structure, and the induc- 

 tion-balance at once afforded evidence of a marked difference 

 not shown in Matthiessen's curve of electric conductivity. 



It is known that certain metals, when alloyed, undergo a 

 molecular change, and that an allotropic condition may in some 

 cases be induced by alloying a metal with a small quantity of 

 another, facts which w ell deserve minute examination as bearing 

 on the non-elementaiy character of certain metals, which is now 

 receiving so much attention. 



Mr. Roberts then referred to the question of applying the 

 induction-balance to the assay of metals. In the case of gold- 

 tilver alloys the instrument will show the presence of less than 

 two grains of gold in the pound of silver. On the other hand, 

 the silver-copper alloys used for coinage are situated at the flat 

 portion of the curve, so that it is impossible to detect even con- 

 siderable differences in their composition, and these alloys which 

 are very peculiar to their nature, appear to be greatly affected 

 by annealing. More hopeful results ^^ere obtained with the 

 gold-copper alloys, and Mr. Roberts demonstrated a difference 

 ■of I per cent, in the standard of two gold disks, which, though 

 far short of the existing method of assay in delicacy, appeared 

 to afford grounds ftr the belief that very accurate results will 

 ultimately be obtained. 



Notes on Pdnleiim Spirit or Benzoliue, by A. II. Allen. — 

 The application of the commercial names "benzoline" and 

 " benzine" to the more volatile portion of petroleum has led to 

 great confusion bet« een petroleum spirit and coal-tar naphtha, 

 the most characteristic constituent of \\ hich is the hydrocarbon 

 benzene or benzol. In this paper the author mentions several 

 tests for distinguishing between the two bodies, the most im- 

 portant of which are the follow ing : — 



Petroleum Spirit, " Benzoline or Benzine," wsxraeCL with four 

 Jneasures of nitric acid of 1 '45 sp. gravity the acid is coloured 

 brown, but the spirit is little acted on, and forms an upper layer. 



Coal-Tar Naphtha or " Benzol" is completely miscible with 

 four measures of nitric acid of r45 sp. gravity, with great rise 

 of temperature and production of dark brown colour. 



These tests are capable of yield ng quantitative results if the 

 treatment with nitric acid be conducted in a small flask and an 

 inverted condenser attached, to prevent loss of vapours. When 

 action has nearly ceased, if the liquid be poured into a narrow 

 graduated tube, the measure of the upper layer indicates with 

 approximate accuracy the amount of petroleum spirit present. 

 If the proportion of benzene is considerable, the nitrobenzene 

 produced may not remain completely dissolved in the nitric acid, 

 in which case it rises and forms a layer of a dark brown colour 

 below the stratum of petroleum spirit. Nitrobenzene and petro- 

 leum spirit are readily miscible in the absence of nitric acid, but 

 agitation with strong nitric acid dissolves out the nitrobenzene, a 

 portion of which may rise and form an intermediate layer as 

 above described. 



By fractional distillation, the author found that the pro- 

 portion of heptane, Cylljj, present in commercial benzoline 

 probably equalled, or even exceeded, that of all the other con- 

 stituents. 



On some Curious Co>urdicn Balls derived from a Colliery 

 Mineral Water, by Thomas Andrews, F.C.S. — The water on 

 which these observations were made was collected from the 

 " sump " of the Wortley Silkstone Colliery, a small pit situated 

 near the "Bassett"or " outcrop " of the great Silkstone seam 

 of coal, the samples being obtained during typical dry and rainy 

 seasons. The water had percolated from the surface a distance 

 of thirty-five yards, through strata, as indicated on the accom- 

 panying table. 



The bottom layer in which the water lodged was the Silkstone 

 seam of coal, here some five feet in thickness. 



One noticeable feature of this water is that it always gives an 

 ■Jlcid reaction with blue litmus paper. 



Several analyses of this water made at various times indicate 



that the chief mineral constituents of the water are, iron — 

 calcium, magnesium, in the form of sulphates. 



This water when heated quickly throws down a copious 

 ochreous deposit. The deposit found in the engine boilers, after 

 having used the water in them for steam purposes was of the 

 composition given below. 



The boiler residue from which this sample was taken consisted 

 of an incrustation al)cut one inch thick, which had adhered to 

 the bottom of the boiler. 



The incrustation was of a light reddish yellow colour in the 

 bulk, it was very hard and tough, and not easily broken in 

 pieces. 



The iron work in connection with this colliery engine and 

 boilers, in any way exposed to the action of either the acid water 

 itself or the steam generated from it, becomes corroded and 

 partially dissolved. The most effectual remedy against this cor- 

 rosive action and deposit is that described in my letter to th« 

 CItemical News, June 15, 1877. 



Some curious balls of mineral matter are occasionally found in 

 the feed tank of the colliery boilers, which are supplied with 

 this water. The w ater is pumped up from the engine pond into 

 a cylindrical feed tank, and is there heated by the exhaust steam 

 from the engine playing on its surface (not blowing through it)-. 

 The water in this feed tank has an average temperature of 

 164° F. 



It sometimes happens that during the short space of even two 

 or three weeks, great numbers of these balls are formed, varying 

 in size from about three and a half inches in diameter to five- 

 eighths of an inch diameter, ar.d in weight from about one and a 

 half ],ound to a quarter of an ounce. 



The author has many of these in his possession. They are 

 perfectly hard and compact when taken from the tank, and are, 

 no fioubt, formed from the deposit thrown down when the 

 mineral water is heated. 



The action of steam playing on the surface of the water 

 probably causes circular eddies, and when a nucleus has thus 

 once been formed, it is easy to conceive of the gradual formation 

 and consolidation of these balls. 



The author suggests that the conditions of formation of natura) 

 nodules of iron ore, pyrolusite, &c., may be similar to those 

 observed by him in the foregoing cases. 



On the Detection of Milk Adulteration, by William H. Wat- 

 son, F.C.S., &c. — From analyses of milk from various dairies, 

 and by a comparison of the results obtained with circumstance* 

 existing as to the character and quantity of the food ; nature of 

 different cows ; conditions and health of them at particular 

 periods ; and changes of the seasons of the year, the author 

 concludes that cows' milk is subject to considerable variations ia 

 composition. He has found, in many instances, milk from 

 well-fed healthy cows to contain as little as io"S per cent, of 

 total solids, and from 8"5 to 9 per cent, of solids not fat. The 

 results of other experimenters are compared, and it is then 

 suggested that fce present limits adopted by public analysts for 

 genuine milk should be reconsidered. 



SECTION C— Geology 



On the Volcanic Products of the Deep Sea of the Central Pacific, 

 with Reference to the " Challtnger " Expedition, by the Abbe A- 

 Kenard and J. Murray. — The mineralogical and petrological re- 

 searches on the sea-bottom of the Pacific area, extending from 

 the Saiidnich Islands to 30° S. lat., and having the Low Archi- 

 pelago on its approximate centre, show that volcanic matter 

 plays an imiiortant part there. It is present in ihe form of 

 lapilli and of ashes spread iu great abundance in the "red 

 clay." These lapilli nearly all belong to the basaltic type, 

 passing from the felspathic basalts to allied rocks, in which the 

 vitreous base assumes greater and greater development, until it 

 almost completely displaces the crystalline constituents of basalt. 

 The fragments then become mere glassy rocks of the basic series, 

 in w hich generally are still found crystals of peridote and num- 

 berless crystallites, which are sometimes grouped in opaque 

 granules, or arranged regularly around the microliths of peridote. 

 The forms of these volcanic fragments, which are often coated 

 with manganese, their association w ith volcanic ash, and their 

 lithological constitution, show them not to be derived from sub- 

 marine flows of lava. They must rather be regarded as incoherent 

 products, or lapilli, the accuu ulations of which in the Pacific 

 form a series of submarine tuffs. One of the most remarkable 

 facts elicited by the soundings in the Pacific is the large share 



