HARD WICKE'S S CIENCE- G OSS I P. 



199 



invite Canada and the United States to do for their 

 respective countries what this Committee has done 

 and is doing in the British Isles. 



I am very cautious in advocating Government 

 endowment of scientific research, knowing how liable 

 it is to abuse, and firmly believing that scientific 

 poverty is preferable to questionably gotten scientific 

 wealth ; but here is a case where the physical welfare 

 and, I may add as a clencher, even the ultra-sacred 

 pockets of the whole community is concerned. We 

 are paying exorbitantly for polluted surface water, 

 imperfectly filtered by pettyfogging artificial filter- 

 beds, while under our feet are vast supplies of 

 nature-filtered water. The primary questions as to 

 the quantity and distribution of this water, and its 

 practical availability for our sore requirements, can 

 only be determined by such work, and is being done 

 by this committee ; therefore, say I, this committee, 

 justly regarded, is a national institution, like the 

 army and navy, and should be supported accordingly. 



The Boulder Committee still continues adding to 

 the details of its curious history of the resting places, 

 dimensions, and composition of wandering blocks of 

 stone. There is one element of cruelty in their 

 proceedings. They are cutting and maiming and 

 murdering the old traditions concerning the giants 

 who carried these stones about, and even damaging 

 the Druids. There is an interesting element of 

 observation in some of these fables. When living 

 at Caergwrle, in Flintshire, I amused myself by 

 studying the glaciation of the district, and succeeded 

 in tracing the limits of a very large glacier, which 

 (in a paper read at the British Association, 1S65) I 

 named the Alyn Glacier, as its boundaries were 

 clearly determined by the same general configuration 

 which determines the curious course of the Alyn 

 river. Among the glacier vestiges is a very large 

 boulder, near the Padeswood station of the Chester 

 and Mold Railway, which bears the name of the 

 " Garreglwyd," or Grey Stone, and gives its name 

 to the farm on which it stands. Another similar 

 stone of smaller size is near to it. Formerly the 

 high-road to Chester passed between these stones, 

 and the tradition states that a Welsh giant, jealous 

 of the growth of Chester, carried these with malig- 

 nant intent towards it ; but, growing tired, dropped 

 them, one on each side of the road. He is said to 

 have brought them from Moel Fammar. They 

 are deeply embedded in soil of glacial origin, 

 overlying carboniferous strata, but are themselves 

 of millstone grit. Moel Fammar is of millstone 

 grit, and eight or nine miles distant. The tradi- 

 tion, therefore, recognises the difference between 

 these and the local sandstones, though my own study 

 of the glaciation connects them with another mass of 

 millstone grit, the Hope Mountain. 



On the 20th of June M. Gaston Tissandier made a 

 balloon trip from Paris to Rheims, in the course of 

 which he obtained 24 instantaneous photographs of 



the country below him. If successful, they must be 

 interesting, but I have not yet met with any account 

 of their publication. The development of aeronauti- 

 cal photography has "considerable scientific interest. 

 Besides supplying us with actual bird's-eye views of 

 known country, with interesting effects ot radial 

 perspective, it will probably be useful hereafter in 

 geographical exploration, an application of ballooning 

 that I have frequently advocated, and believe will be 

 very successfully used when we have so far perfected 

 the fabric and varnish of the body of the balloon as to 

 prevent the exosmosis of the gas, which now limits 

 the period of possible flotation of the machine to only 

 a few hours. With this one defect remedied, and the 

 waste of ballast obviated by the use of the drag rope, 

 days may replace hours in balloon voyages, especially 

 within the Arctic Circle, where the summer daylight 

 is continuous. 



A correspondent writing from Kashmir (G.M.G.), 

 asks why corrections for temperature are added to 

 the tables for determining elevations above the sea 

 by observations on the boiling point of water. In 

 reply, I ask him to consider why water boils at a 

 lower and lower temperature as we ascend. He will 

 easily understand that this is due to diminished 

 atmospheric pressure, and that this diminution of 

 pressure is a consequence of our leaving below us a 

 larger and larger fraction of the whole atmosphere as 

 we rise higher and higher. But the quantity thus 

 left below for every hundred feet (or other unit) of 

 ascent must depend upon its density : this density 

 diminishes as the temperature of the air increases, 

 and therefore if he climbs 100 feet on the hill side, 

 from the valley of Kashmir, in the midst of air at 

 8o° Fahr., he will have left less air below him than I 

 should leave behind me in climbing 100 feet from a 

 starting point of similar elevation on the side of 

 Snowdon, in the midst of air at a temperature of 50 . 

 Or, otherwise stated, his atmosphere at Kashmir, 

 being warmer than ours here, is proportionally taller, 

 pressure at base being the same. The same correction 

 for temperature is of course required in measuring 

 heights by means of the barometer. 



In my last month's gossip I referred to Professor 

 Langley's lecture at the Royal Institution, and 

 attributed his startling conclusion concerning the 

 effect of solar radiation on a planet unprotected by 

 atmospheric resistance to a verbal ambiguity in the 

 report of the lecture, but now find that I was 

 mistaken ; that Professor Langley really does mean 

 that such direct unimpeded radiation would fail to 

 warm the surface of such a planet up to the freezing 

 point of mercury. I learn this from the quarto 

 volume describing his " Researches on Solar Heat, 

 and its Absorption by the Earth's Atmosphere," which 

 he has kindly sent me. In spite of my great respect 

 for Professor Langley and his valuable work, I am 

 satisfied that he is wrong on this point, though pro- 

 bably right as regards his high valuation of the solar 



