fifths. But it seems to me that this rule can hardly be very accurate, and that it would be desirable to find the mean velocity by the use of a current metre, working in different parts of the section. However, this element once determined, it is of course only necessary to multiply the area of the section in feet, by the mean velocity in feet for a given time, to ascertain the number of cubic feet which flow past in that time. 3rd. The proportion of sediment held in suspension is ascertained by collecting a certain measure of water (a quart bottle answers the purpose very well), and then decanting and filtering it. If the filter be carefully dried and weighed, before and after the experiment, the difference gives the weight of mud from which the per centage of grains to ounces of water can be obtained. We shall now have sufficient data to determine how much solid matter passes down the river in a given time at any flood. 4th. Besides these observations, the rainfall at different points of the watershed of the river should be carefully registered. Thus some correlation between the two could probably be ascertained, so that from year to year an average rate of the wear and tear of the surface of the land might be obtained. Many subjects of interest will naturally suggest themselves as we proceed with these experiments, such as the variation of the sediment after a long drought, and after a continued fall of rain. Of the above data, the most unsatisfactory are those relating to the mean velocity of the stream at different heights. Perhaps some of your readers may be able to furnish suggestions upon the best mode of ascertaining this. Besides the mud actually held in suspension, it would be very desirable to determine the rate at which the mud, sand, and gravel which compose the bed of the river are propelled. Some suggestions on the means of doing so would be very acceptable. STOKESAY, CRAVEN ARMS, SALOP, THE V. ON THE INFLUENCE OF THE GULF-STREAM. By JAMES CROLL, of the Geological Survey of Scotland. THE modern method of determining the amount of heat effects in absolute measure is no doubt destined to cast new light on all questions connected with climate, as it has done and is still doing in every department of physics where energy under the form of heat is the phenomenon under consideration. Owing to the complicated nature of the phenomena with which the meteorologist has generally to deal, the application of this method will very often be found practically impossible. The method, however, is particularly suitable to all questions regarding the direct thermal effects of currents, whatever the nature of those currents may happen to be. If the question, for example, is asked-"Is the heat conveyed by the Gulf-stream sufficient to affect to any great extent the climate of Northern Europe and the Arctic regions?" the answer can be given in the most positive manner by determining the absolute quantity of energy in the form of heat conveyed by the stream. The fact of the climate of our island being greatly modified by the heat derived from the Gulf-stream has lately been called in question by Mr. A. G. Findlay and some others. Mr. Findlay takes the breadth of the stream, as it issues from the Gulf of Mexico, at 45 miles, and its depth at 900 or 1200 feet, and maintains that a stream of this size, leaving the Gulf with a velocity of only a few miles an hour, would not be able to force itself across the Atlantic and onwards to the Polar Regions against the Arctic current and other impediments in its way; and even supposing it were able to do this, still its volume, he asserts, is too small and its temperature too low to produce the thermal effects attributed to it. It is certainly, no doubt, true that if the Arctic current was an opposing current as well as a contrary one, and if the Gulf-stream had to push its way to the Polar Regions by means of some impulse received before leaving the Gulf, it is not at all likely that it would ever reach to even the latitude of New York, far less to the shores of Great Britain. But neither the Gulf-stream nor any other ocean current moves in this manner. It is, however, not with this phase of the objection that I am at present concerned, but with the other and more important one, viz. that a current 45 miles broad and 900 or 1200 feet deep is too small to convey the amount of heat necessary to produce the warming effects usually attributed to the Gulf-stream. There are perhaps few, if any, who have not actually subjected the matter to calculation, but would be inclined to agree with Mr. Findlay, that a stream so comparatively small, leaving the Gulf of Mexico at a temperature of not over 70° or 80°, and losing heat during a journey of several months across the Atlantic, could not possibly be able to maintain the winter temperature of the whole of Northern Europe 20° or more above the normal. They would naturally conclude that the only way of meeting Mr. Findlay's objection would be by denying that the stream is so small as he asserts it to be. Although I am inclined to believe that Mr. Findlay has underestimated the volume of the Gulf-stream, still I can see no necessity for insisting on this in order to be able completely to meet his objection; for, taking his estimate of its size, it can be proved that his conclusion is incorrect, as the following, it is hoped, will show. In the following calculations the breadth of the stream is taken at 50 miles, and its depth at 1000 feet, and its velocity at four miles an hour. This is almost exactly Mr. Findlay's estimate. The temperature of the water on leaving the Gulf is taken as low as 65°. "The enormous effect that ocean-currents have in equalising the temperature of our globe by diminishing the difference between the temperature of the equator and the poles, has never been duly estimated. This will be seen if we merely consider for a moment the effect produced by one current alone, viz., the Gulf-stream. The total quantity of water conveyed by this stream is probably equal to |