EDMUND HALLEY was a very great man. He was not only the first to predict correctly the return of a comet, that which is now known by his name, but also—before Newton had announced his results to any one—arrived at the conclusion that the attraction of gravitation probably varied inversely as the square of the distance. While these and other important achievements of his are well known, it seems to have been forgotten that Halley devised a method of determining the age of the ocean from chemical denudation. Indeed, I find no mention of Halley in the indices of some of the most authoritative works on geology and geochemistry, while it is evident that neither Mr. T. Mellard Reade * nor Mr. J. Joly f was aware of a predecessor in this important field. It was almost by accident that I came across Halley's paper read before the Royal Society in 1715, extracts from which are given below. Halley recognized that the method as he proposed it was almost impracticable, but writing as he did twenty-eight years before Lavoisier's birth, he could hardly have guessed that accurate analyses of river waters, whose solvent action he so clearly describes, would ever become not merely possible but easy. It is very interesting to note that Halley's reasoning is strictly “uniformitarian” while he recognized the tendency involved to a maximum estimate. Subject to this same limitation (extended to other features besides an original saltness of the sea), Mr. Joly's method of determining the rate at which the accumulation of salt in the ocean takes place from the analysis of river waters is perhaps the most important means now available for an estimate of the antiquity of the stratified rocks, because it is the simplest and least open to question. To my thinking the fact that his train of reasoning coincided with that of the great astronomer only adds to the credit due Mr. Joly. A great amount of work has been done of late years on the composition of river waters, much of it incited by Mr. Joly's memoir and undertaken with the purpose of improving the data for such a determination of the age of the ocean. Within a few months it will be practicable to make known the results of a revised estimate founded upon data far more ample than those at the disposition of Mr. Joly eleven years ago. Mr. K\ W. Clarke is now engaged in preparing this estimate. The subjoined extracts from Halley's paper i cannot but interest all lovers of natural science: “On the Cause of the Saltness of the Ocean, and of the Several Lakes that Emit no Rivers; with a Proposal, by Means Thereof, to Discover the Age of the World. There have been many attempts made, and proposals offered, to ascertain from the appearances of nature, what may have been the antiquity of this globe of earth; on which, by the evidence of sacred writ, mankind has dwelt about 6,000 years; or according to the Septuagint above 7,000.... This inquiry seeming to me well to deserve consideration, and worthy the thoughts of the Royal Society, 1 shall take leave to propose an expedient for determining * u Chemical Denudation in Relation to Geological Time,' 1 1879, t Trans. R. S. Dublin, vol. i., 1899, p. 23. t Phil. Trans., yol. xsix., 1715, p. 296. the age of the world by a medium, as I take it, wholly new, and which in my opinion seems to promise success, though the event can not be judged of till after a long period of time; submitting the same to their better judgment. What suggested this notion was an observation I had made, that all the lakes in the world, properly so called, are found to be salt, some more, some less than the ocean, which in the present case may also be esteemed a lake; since by that term I mean such standing waters as perpetually receive rivers running into them, and have no exit or evacuation.... Now 1 conceive that as all these lakes receive rivers, and have no exit or discharge, so it will be necessary that their waters rise and cover the land, until such time as their surfaces are sufficiently extended, so as to exhale in vapor that water which is poured in by the rivers; and consequently that lakes must be larger or smaller, according to the quantity of the fresh they receive. But the vapors thus exhaled are perfectly fresh; so that the saline particles brought in by the rivers remain behind, while the fresh evaporates; and hence it is evident that the salt in the lakes will be continually augmented, and the water grow Salter and Salter.... Now if this be the true reason of the saltness of these lakes, it is not improbable but that the ocean itself is become salt from the same cause, and we are thereby furnished with an argument for estimating the duration of all things, from an observation of the increment of saltness in their waters. For if it be observed what quantity of salt is at present contained in a certain weight of the water, of the Caspian Sea, for example, taken at a certain place, in the driest weather; and after some centuries of years the same weight of water, taken in the same place, and under the same circumstances, be found to contain a sensibly greater quantity of salt than at the time of the first experiment, we may by the rule of proportion, make an estimate of the whole time wherein the water would acquire its present degree of saltness. And this argument would be the more conclusive, if by a like experiment a similar increase in the saltness of the ocean should be observed; for that, after the same manner as aforesaid, receives innumerable rivers, all which deposit their saline particles therein; and are again supplied, as I have elsewhere showed, by the vapors of the ocean, which rise from it in atoms of pure water, without the least admixture of salt. But the rivers in their long passage over the earth imbibe some of its saline particles, though in so small a quantity as not to be perceived, unless in these their depositories after a long tract of time. And if, on repeating the experiment, after another equal number of age's, it shall be found that the saltness is further increased with the same increment as before, then what is now proposed as hypothetical, would appear little less than demonstrative. But since this argument can be of no use to ourselves, it requiring very great intervals of time to come to our conclusion, it were to be wished that the ancient Greek and Latin authors had delivered down to us the degree of the saltness of the sea, as it was about 2.000 years ago; for then it cannot be doubted but that the difference between what is now found and wliat then was, would become very sensible. I recommend it therefore to the society, as opportunity shall offer, to procure the experiments to be made of the present degree of saltness of the ocean, and of as many of these lakes as can be come at, that they may stand upon record for the benefit of future ages. “If it be objected that the water of the ocean, and perhaps of some of these lakes, might at the first beginning of things, in some measure contain salt, so as to disturb the proportionality of the increase of saltness in them I will not dispute it; but shall observe that such a supposition would by so much contract the age of the world, within the date to be derived from the foregoing argument, which is chiefly intended to refute the ancient notion some have of late entertained, of the eternity of all things; though perhaps by it the world be found much older than many have hitherto imagined.” The Boston Elevated Railway Company has begun to hold regular monthly meetings of the chief engineers of its power stations, corresponding to the meetings which the company also holds with its division superintendents and car-house foremen. It is proposed to appoint subjects for discussion which will lead toward a reduction in operating costs and the improvement of the power station service in general. Tabulations of the cost of production at the different plants will be prepared regularly, including comparisons of the current performance of each station with previous operation, and the contrasting of conditions and operating results in the several plants. The company at present operates eight steam and two gas engine plants of a normal capacity of 50,000 kilowatts. The operations of these stations are under the jurisdiction of a superintendent of power stations, reporting to the chief engineer of motive power and rolling stock. At the initial meeting in April a general discussion of operating conditions in the different plants was held, after which the purpose of the meetings was explained by the chief engineer of motive power and rolling stock. The purchase of coal on its heating value by the United States government is reported, by the Technologic Branch of the United States Geological Survey, to have effected a saving of $200,000 in the annual fuel bill of the government, which now aggregates about $1,000,000. At the present time, forty departmental buildings in Washington, more than three hundred public buildings throughout the United States, the Panama Railway, navy yards and arsenals are buying their fuel supplies on specifications fixing the amount of ash and moisture. The actual (uiality and value of the coal delivered is determined by analyses of representative samples and deductions are made from the contract price, in case of deliveries cf poor coal, proportionate to the decrease in heating value. Premiums are paid for any decrease of ash greater than 2 per cent below the specified amount at a rate of 1 cent per ton for each per cent, and deductions are made at an increasing rate for each per cent of ash in excess of 2 per cent above the standard.