570 



NATURE 



{April 



attention, by short lectures to the fishermen, conversations with 

 them, and otherwise, to awaken an interest in weather forecasts 

 and their intelligent interpretation. Though the giving of the 

 lectures is practically limited to the Saturdays, when the fisher- 

 men are disengaged, yet opportunity was taken to deliver eleven 

 lectures, which were attended by audiences varying from 40 

 to 250. The method of proceeding was to give, by the help of 

 weather charts, a short explanation of the law of storms, and an 

 account of the weather of the week immediately preceding the 

 lecture. The fishermen were then invited to ask questions, and 

 raise discussions on the subjects of lecture. 



During the winter Prof Balfour engaged Mr. Turnbull to give 

 fourteen lectures to the employees of the Garden on meteorology, 

 in which marked prominence was given to the practical side of 

 the science, explaining and teaching them to handle each instru- 

 ment — why it is placed in the position it occupies, and not 

 elsewhere ; and showing the methods of reducing the observa- 

 tions. The efficient training of a body of men from which the 

 Council largely draws its observers is a matter of no small 

 importance. A suitable site has been procured in Fort William 

 for the proposed low- level observatory, and plans of the build- 

 ings prepared by their architect, Mr. Sydney Mitchell, and 

 submitted to the Directors and the Meteorological Council, and 

 approved of. The plans and specifications are at present in the 

 hands of the contractors, and the building will forthwith be 

 commenced. 



Mr. Herbertson exhibited to the meeting an instrument, 

 named the stephanome, designed by Prof. Tait, for use at the 

 Ben Nevis Observatory for measuring the angular size of halos, 

 fog-bows, glories, &c. ; also a valuable collection of sixteen 

 photographs taken at the Observatory, of which the following 

 are of special interest ; a cirrus cloud in the northern horizon, 

 taken at midnight in June, when the clouds are seen to be 

 brightly illuminated ; St Elmo's Fire, at it p.m. on the top of 

 the stove-pipe ; and views of the Observatory after continued 

 fog and strong wind, but no fall of snow, when everything is 

 covered with long crystals of ice formed out of the fog. 



Dr. Buchan read a paper on the distribution of storms round 

 the Scottish coasts, based on the observations made at the 

 lighthouses during the past seven years. The year is divided by 

 the equinoxes into two strongly contrasted portions as regards 

 storms of wind. The minimum occurs in July, and the maximum 

 in January. Over the whole country there is an annual average 

 of 431 hours of storm occurrence. Dividing Scotland into seven 

 districts, the following is the order of occurrence : Firth of Clyde, 

 327 hours ; Tweed to Aberdeen, 373 hours ; Aberdeen to 

 Caithness, 379 hours ; Fort William to Islay, 408 hours ; Cape 

 Wrath to Mull, 435 hours ; the Irish Sea, 508 hours ; and 

 Orkney and Shetland, 562 hours. From a report prepared by 

 Mr. Omond it appears that, on an average of the past five years, 

 the wind at the Ben Nevis Observatory has risen to or exceeded 

 the rate of 45 miles an hour, 849 hours per annum. 



Mr. H. N. Dickson read a paper on " The Weather Lore of 

 Scottish Fishermen." The fishermen had a very complete and 

 generally accurate knowledge of weather phenomena as far as 

 it was purely a matter of observation. In the course of his in- 

 quiries he had got a great deal of miscellaneous information from 

 them on prognostications. The prognostications which received 

 the greatest acceptance among the fishermen were those of 

 halo, coronre, and mock sunrises. It is a belief current from 

 Aberdeen to Wick that, if a sun-dog preceded the sun, it was a 

 sign of good weather, but if it followed the sun it was a sign of 

 bad weather. Another very general belief in prognostications 

 was the existence of spiders' webs amongst the cordage of ships 

 and in sails. That was a very general belief all along the coast. 

 There was another prognostication which was currently believed 

 in by the fishermen, taken from the occurrence of broken rain- 

 bows, which are called "packmen," from the fact that the 

 packmen sold pieces of coloured ribbon. As regards the cirrus 

 cloud, in Shetland and Orkney and on certain parts of the west 

 coast, but not on the east coast, there was an almost universal 

 belief in "weather-heads." If these "weather-heads" ran in 

 the direction of north-east to south-west, it was a sign of good 

 weather, but if it ran south-east to north-west, it was an 

 unfavourable sign. If the aurora rises in the north, and 

 does not come past the zenith, it is a sign of good 

 weather ; but should the streamer extend beyond, a gale 

 of south wind is expected. The only other point with regard 

 to the aurora was that in Shetland it was supposed to be 

 near a very severe gale if the aurora emitted a sound resem- 



bling the shaking of a blanket. Another prognostication, very 

 interesting in its way, and which all fishermen had seen, is the 

 " false dawn." The " false dawn " was when the dawn seemed 

 to break, and then disappeared. There was some question as to 

 whether it was a prognostication. At St. Andrews they were 

 almost unanimous in believing it as a prognostication, and in 

 other places he got individuals who believed it was a sign of 

 good or bad weather. It was interesting in this way that he 

 had never heard of the " false dawn " as a prognostication before, 

 and he made some investigations as to whether it was common in 

 other parts of the world, and he found it was also current 

 among the Negroes of South America. In Shetland there was 

 a class of prognostications which did not appear anywhere 

 else. It was a sign of a coming gale if the surface of the water 

 became stiff and bubbles remained in the wake of a boat, and 

 if the wake of a boat remained visible for an unusually 

 long time. Another prognostication was known as 

 " cheepers." A sound was heard as if a lot of little birds were 

 floating above the boat, and gave a sort of cheeping sound. 

 That was also called "foul air" by another class of fishermen. 

 In the Outer Hebrides the state of the air was almost the only 

 thing the men paid attention to. It was current all down the 

 west coast that a heavy surf was the sign of a gale approaching, 

 but on the east coast one did not hear much of the heavy surf. 

 He had found among the fishermen much less superstition than 

 they usually got credit for, especially at the largest stations. In 

 the smaller stations, where the boats were very small, there was 

 still a good deal of superstition. In the larger stations, where 

 the boats were large and the nien went far out to sea, there was 

 a great deal of faith in weather prognostications and a strong 

 desire for instruction. 



Mr. H. N. Dickson also added a note on the temperature of 

 the water round the east coast of Scotland. The curve of the 

 daily variation of temperature in the North Sea was as nearly as 

 possible symmetrical above and below the mean. That was the 

 case where there was reason to believe the water was almost 

 stationary. In observations taken in the North Atlantic and on 

 the west coast of Scotland in warm currents of water, as long as 

 the curve was below the mean, it was almost quite straight, and 

 when above the mean the maximum was intensified and 

 sharpened. In observations taken in the cold Polar current off 

 the Island of Jan Mayen the opposite was the case, the curve 

 being deep below the mean and flat above it . 



Mr. Philip Sewell gave a few notes of a voyaT;e he made to 

 Siberia last summer. From the temperature observations and 

 other information submitted, he considered trading to the 

 mouths of the Obi and Yenissei to be practicable in ordinary 

 summers. 



TWO-NOSED CA TEN ARIES} 



T^HE curve to be given to an ideal linear chain or rib under 

 -'- uniform-vertical-load area between itself and a horizontal 

 straight line is well known to be a Transformed Catenary, 

 having iis ordinates in a constant ratio to the corresponding 

 ordinates of a Common Catenary inverted, with the horizontal 

 straight line as directrix (Rankine, "Civil Engineering"; 

 Church, " Mechanics of Materials," &c. ). 



Thus, the equation of the Common Catenary being — 



-^= cosh "'^, 

 m m 



using the notation of the hyperbolic functions, then the equation 

 of the Transformed Catenary will be — 



y _ 



r cosh -, 



;- being a fraction, greater or less than unity. 



The authors of^ this paper appear to have been the first to 

 notice the elegant mathematical fact that, for values of r 

 numerically less than ^3 = 0-577, the Transformed Catenary 

 possesses two points, equidistant from the vertex, at which the 

 curvature is a maximum ; so that in the j^ractical design of 

 masonry arches, which are almost always made circular, a better 



■ "Two-Nosed Catenaries and their Application to the Design of Seg- 

 mental Arches." By T. Alexander, C.E., Professor of Engineering, Trinity 

 College, Dublin, and A. W. Thomson, B.Sc, A.M.I.C E., Lecturer in the 

 Glasgow and West of Scotland Technical College. (From the 'transactions 

 of the Royal Irish Academy, vol. x.xix. Part 3, 1888 ) 



