June 7, 1889.] 



SCIENCE 



435' 



Another very important fact (established by Meldrum at Mauri- 

 tius) may be stated thus : When a hurricane is moving along the 

 equatorial limits of a trade-wind region, there is a belt of intensi- 

 fied trades to windward of its track. Not until the barometer has 

 fallen about six-tenths of an inch is it safe to assume, that, be- 

 cause the trade-wind' increases in force and remains steady in 



i>iagiam'Na,:.3.' 



Iuna"'& Oct.. lal.'23' 



io.55: 

 July, & 



to 55.' 

 Aiigy Jat. 



to 55° 



N.N.E- — ^^'Jfc, yebcit)- oTan. 

 E _ ~ lo ^ track 



' • jicrhoui 



Teloci^^ cthrng tracfn 

 pef 



gtoBJiHTIj^pt. Diagram No, 2. 



.»<»*''■" Mc' 'Vj/. Juue and Oct., latitude 



s. risi -^t 2(P to 23° in 



July and Sept., latitude 

 ^ "— to2f)°N. 



iug., latitude 

 30° to 33° S". 



abaut77miLes 

 "per hour. 



Diagram No. 1, 



The small arrows fly with thi 

 join points having 

 isobars, the barometer fallin^ 

 The shaded area is the region where i 

 age size of one of these storms in diffe: 

 the scale of miles accompanying each d 



1. The 

 be estimated by i 



direction, you are on the track of the storm. By attempting too 

 early to cross its track, running free as soon as the wind begins to 

 freshen, you are liable to plunge directly into the vortex of the 

 hurricane. 



Brief rules for action are the following : Watch carefully for the 

 earliest indications, recording observations of barometer, ther- 

 mometers, wind and weather, for future reference. When there is 



good reason to suspect that a hurricane is approaching, consider 

 the latitude you are in, and the month, with a view to decide the 

 probable direction in which the storm is moving, and when its 

 track is likely to recurve. Early action may thus be taken to avoid- 

 its path. When the decided fall of the barometer, freshening rain- 

 squalls, and other unmistakable signs, indicate that the cyclone is 

 close upon you, observe the shifts of wind very carefully, in order to 

 determine whether you are to the right or left of the storm-track. 

 Remember that it is sometimes best to lie to when thus observing 

 the shifts of wind. A fast steamer, for instance, may run into the 

 dangerous semicircle of a slow-moving cyclone, and yet get shifts 

 of wind characteristic of the navigable semicircle. If the freshen- 

 ing gale remain steady in direction, you are on the track of the 

 advancing storm : square away, at all hazards, and run with the 

 wind on the starboard quarter, keeping your compass course as the 

 wind shifts ; if obliged to lie to, do so on the port tack. If the 

 wind shift to the right, you are to the right of the storm-track : put 

 the ship on the starboard tack, and make as much headway as- 

 possible ; if obliged to lie to, do so on the starboard tack. If the 

 wind shift to the left, you are to the left of the storm-track : bring 

 the wind on the starboard quarter, and keep your compass course, 

 if possible ; if obliged to lie to, do so on the port tack. Any 

 attempt to cross the storm-track is dangerous ; but, if you decide 

 that it must be attempted, crowd sail and keep the wind well on 

 the starboard quarter. In scudding, always keep the wind well on 

 the starboard quarter, in order to run out of the storm. If obliged 

 to lie to, always do so on the coming-up tack, so that the wind will 

 shift aft, and not take you aback. Should you get into the central 

 calm of a tropical cyclone, look out for a terrific squall from a point 

 of the compass almost exactly opposite to that from which tlie. 

 wind was blowing when it fell calm. 



So long as the barometer continues to fall, the centre is getting 

 nearer. When it steadies and begins to rise, this marks the near- 

 est point; and here the shifts of wind will be most sudden and 

 violent, and the sea highest and most confused. If, when lying to,, 

 the wind begins to shift in the opposite direction to what it did at 

 first, it is evidence that the storm-track is recurving, and your 

 semicircle is changed : immediate action must be taken to suit the- 

 new conditions. But if your vessel is making any great headway, 

 it may give you a shift of wind contrary to what you would have if 

 lying to : this must be always borne in mind. Cool weather is 

 characteristic, in extra-tropical regions, of the navigable semicircle, 

 owing to the indraught from the north-westward ; warm weather, on 

 the contrary, indicates the dangerous semicircle, where the air is, 

 drawn in from the south-eastward. 



After encountering a hurricane in the tropics, a northward-bound' 

 vessel is very liable to encounter the same storm again in higher 

 latitudes, after it has recurved. The navigator should therefore 

 remember that there is a hurricane off to the westward, and look- 

 out for it as he goes north. 



There are two cyclone currents to be considered, — a current 

 moving in a circular direction around the centre, caused by the- 

 wind ; and a current which follows the storm along its track- 

 These vary considerably with different storms, but should always 

 be taken into account when near the coast. 



The testimony as to the great value of the use of oil in heavy- 

 seas is so conclusive that it is now recognized by every commerciat 

 nation. No ship can afford to neglect its use in an emergency,, 

 when heavy broken seas threaten to come on board. Once tried,, 

 its value will never be disputed. Fifty-four reports have already- 

 been received this year from masters of vessels who have used oil 

 with great success : thirteen of these refer to a single storm, the 

 hurricane off Hatteras, April 6-9, and new reports are received 

 almost every day. 



ELECTRICAL NEWS. 



The Average Efficiency of Incandescent Lamps. 



At the meeting of the Institute of Electrical Engineers, held on 

 May 22, Mr. W. H. Peirce read a paper under the title " Relation 

 between the Initial and Average Efficiency of Incandescent Elec- 

 tric Lamps," which gave the results of experiments made by 

 him for the Chicago, Burlington, and Quincy Railroad. Four 



