Sept. 14, 1888.] 



SCIENTIFIC NEWS. 



>8 5 



A hurricane was also always changing its shape, so that the oval lay 

 sometimes in one way, and sometimes quite in a different direction ; 

 while sometimes the vortex was displaced towards one side of the 

 oval one day, and towards quite another side on the next. 



The path of the hurricane was not in a regular line, for the vortex 

 sways about, and sometimes even described a loop. 



For all these reasons, no rule was possible for determining 

 absolutely the bearing of the vortex by observations on board a 

 single ship, whereas it used to be stated positively that facing the 

 wind the vortex bore 8 points— at right angles — to the right in the 

 Northern, and to the left in the Southern Hemisphere. 



It can only be said now that, when fairly within the storm-fit Id and 

 facing the wind, the vortex will be to the right and a little to the 

 rear— that was, from 8 to 12 points to the right of the wind — in the 

 Northern Hemisphere, and to the left and a little to the rear — that 

 was, from 8 to 12 points to the left of the wind — in the Southern 

 Hemisphere. If the wind blew exactly in a circle round a circular 

 hurricane the vortex would always bear 8 points to the right or left 

 according to the hemisphere, and the rule to take 8 to 12 points is 

 simply allowing for the effects of variable incurvature. 



The above rule does very well for a first approximation to the bear- 

 ing of the vortex, but greater precision can be attained in certain 

 circumstances. If the condition indicated that a ship was nearly in 

 front of the vortex the bearing of the vortex will probably not be 

 much more than 8 points to the right or left, according to the hemi- 

 sphere, because, as before mentioned, the incurvature was very small 

 in front of a hurricane. Great care must be taken not to apply this 

 rule to an increasing trade with a falling barometer, as will be ex- 

 plained hereafter. 



In the rear of a hurr.'cane, on the contrary, the vortex might bear 

 12 or even more points to the right or lelt of the wind, because the 

 wind was very much incurved in that part of a hui ricane. A ship 

 should therefore always then lie-to till the barometer began to rise 

 and the weather to improve, otherwise she would probably run right 

 into the vortex. She might easily scud 10 knots, while the hurri- 

 cane might not be advancing more than 5 miles an hour, so that it was 

 very easy to catch up the vortex. The discovery of this great in- 

 curvature is one of the most important modern developments of the 

 subject. 



It used to be thought that if the wind increased in force, without 

 changing in direction, with a falling barometer, a ship must 

 necessarily be in the line of progression of the vortex, and that she 

 should run at once. This was owing to the idea that a hurricane 

 was an isolated disturbance. 



Now we know that if it be only the usual trade-wind, which in- 

 creases without changing in direction, and with a falling barometer, 

 a ship should lie-to till the mercury has fallen at least 6-loths of an 

 inch before she runs as a last resource. Modern research had 

 proved that a hurricane is usually embedded in some prevailing 

 trade or monsoon, and that there was therefore a belt of intensified 

 trade-wind outside the true storm-field. This belt was always on the 

 side of the hurricane farthest from the equator. A ship in this 

 belt experienced an increasing trade without change of direc- 

 tion, and with a falling barometer, though she might be far away 

 from the line of progression of the vortex. She would equally ex- 

 perience an increasing and unchanging wind, with a falling 

 barometer, if she were in ihe line of progression ; but as there was 

 no means of knowing whether she was in the line of progression or 

 only in the belt of intensified trade, the empirical rule says, " Lie- 

 to till the mercury has fallen 6-tenths of an inch before beginning to 

 run." 



The old lules for finding which semicircle of a hurricane a ship 

 may be in, and the old rules for heaving- to in either hemisphere, 

 are all proved to be both tine and valuable by modern research. 

 These rules remain as follows : Facing the wind in both hemi- 

 spheres, if the wind changes by the right the ship is in the right- 

 hand semicircle, and she should heave-to on the starboard tack ; if 

 the wind changes by the left she is in the left semicircle, and 

 should heave-to on the port tack. If circumstances compel her to 

 run she should keep the wind well on the starboard quarter in the 

 North Hemisphere, and well on the port quarter in the South 

 Hemisphere. 



It is much to be regretted that the examination-papers of the 

 Board of Trade for master and mates are painfully behind the 

 modern standards of knowledge, and that in these matters the 

 Germans and other nations are now ahead of England. The whole 

 knowledge which is required in our merchant service is contained in 

 six questions, and a candidate is expected to say that the centre 

 bears S points, or perhaps a l.ttle more, from the direction of the 

 wind, while no notice is taken either of the small incurvature in 

 front or of the great incuivature in rear, or of the belt of intensified 

 trade, ./here the usual indications of being exactly in front of the 

 vortex fail. 



No one should blame the master of a ship for not following the 

 established rules, without the closest investigation, for, as Pidding- 

 ton says, " absolute rules are all nonsense," and much depends on 

 the capabilities of a ship and on the ever-varying conditions of a 

 heavy cross sea. 



Professor Douglas Archibald felt that many vessels had been 

 lost through following strictly antiquated rules. Seamen were 

 rather conservative, and liked to stick to their old rules, but he was 

 of opinion that the sooner the results of modern observation were 

 adopted the better it would be all round. He was sorry that M. 

 Faye and those who thought with him were not present to hear Mr. 

 Abercromby's paper, because he thought they would have found it 

 rather hard to say, in the face of that paper, that there was no such 

 thing as an elliptical hurricane. 



Dr. W. H. Russell desired to ask a question as to the rotatory 

 action of winds. He saw a number of new faces on the plat- 

 form, and he wished to inquire, therefore, if any one could explain 

 why it was that winds were so frequently rotatory in their motion. 



Mr. W. N. Shaw, MA., one of the Secretaries of the section, 

 explained what he considered was the cause of hurricanes having a 

 circular motion. His argument tended to show that rotatory winds 

 were caused by rushes of hot air from one quarter meeting rushes of 

 cold wind from an opposite direction, which caused the rotatory 

 motion the last speaker had inquired about. 



Dr. H. R. Mill then read the report of the Committee on The 

 Surface Temperature of Water, and followed it up by a paper on 

 The Temperature of some Scottish Rivers. 



Professor C. G. Ivnott discoursed on The Recent Magnetic Survey 

 of Japan. He observed that, generally speaking, the magnetic 

 features of Japan present great irregularities — a fact which the 

 highly volcanic condition of the country would lead us to expect. 

 The south western portion of the main island, with the adjacent 

 islands fringing the inland sea, presents fairly uniform magnetic 

 features. The regions where the greatest disturbances exist are (1) 

 the great central mountain region to the north and north-west of 

 Fujiyama, and (2) the region included between the 38th and 40tn 

 parallels of latitude. 



The general characteristics of the iso-magnelic lines correspond- 

 ing to the observations made are as follows : The lines of equal 

 dip, of equal horizontal force, and of equal total force are 

 approximately straight, while the lines of equal declination are 

 distinctly parabolic or hyperbolic, approximating very closely to 

 the general form of the main island. 



The full details of the survey are given in the second volume of 

 the "Journal of the College of Science, Imperial University, 

 Japan," where also will be found the charts, of which the large 

 charts now shown were rough copies. 



Mr. J. Joly lectured on Reading Electrically Meteorological 

 Insti uments Distant from the Observer. 



Mr. W. N. Shaw, in the absence of Professor G. H. Darwin, 

 F.R.S., put before the section the paper of the latter on The 

 Mechanical Condition of a Swarm of Meteorites, and on theories of 

 cosmogony, and then read his own communication on Some Charts 

 of K'ew Corrections for Mercury Thermometers. 



The Committee upon Standard Lights submitted their final 

 report upon this subject. In the course of a lengthy document the 

 Committee stated that they had experimented upon ordinary 

 candles, upon sperm candles (six to the pound), with pentane 

 standard lights, and also with the pentane lamp, and with 

 the amyl-acetate lamp. As the result of the experiments the 

 Committee considered that the standard candle, as defined by 

 Act of Parliament, was not worthy of the present state of 

 science, and they gave their opinion in favour of an altera- 

 tion of the law with regard to standard lights and the adoption of 

 the pentane standard. They further recommended that it should 

 be urged upon the Board of Trade that legislative action should be 

 taken, with a view to speedily bringing about the change suggested' 

 in the report. 



Mr. Wm. Shaw read a paper on An Apparatus for Determining 

 the Temperature by the Variation of Electrical Resistance. 



Tuesday, September iith. 



Professor FitzGerald presiding. 



There was a very large attendance, Section "G" joining with 

 Section " A " to carry on a discussion on 



Lightning-conductors. 



Mr. W. H. Preece, F.R.S., opened the debate. He said that it 

 was a most remarkable thing that if we wanted to know much about 

 atmospheric electricity we had to go back to the days and works of 

 Benjamin Franklin, a hundred and forty years ago. Up to 1878 



