September 22, 19 10] 



NATURE 



0/0 



■_ j>t, and on October 1 1 the barometer at Key West 

 ( Florida Channel) fell to 28-50 inches, the lowest ever 

 recorded there, and more than 6 inches of rain fell in 

 2{ hours, the damage being estimated at nearly a million 

 dollars. The Weather Bureau duly warned the seaports 

 of the progress of the storm, and thereby effected great 

 saving of life ; on the Florida East Coast Railway, for 

 instance, 3000 workmen were withdrawn from dangerous 

 points; and the vice-president of the line writes: — "Posi- 

 tively not a life was lost in the storm. . . . Warning by 

 the Weather Bureau enabled us to fully protect all 

 employes and equipment." 



The Central Weather Bureau at Melbourne has recently 

 issued an average rainfall map and isohyets of New 

 South Wales, the first of a series now in course of pre- 

 paration which will include all the States. These maps 

 will be of great economic value in connection with corn- 

 growing and the keeping of all kinds of stock, for which 

 a knowledge of the rainfall is of prime importance. The 

 map in question clearly shows that the greatest rainfall 

 occurs on and adjacent to the Pacific coast, where the 

 annual amounts range from 30 inches in the south to 

 60 and even 70 inches in the north. The isohyets and 

 grades of shading plainly show the decrease of the rain- 

 fall to the westward. If a 15-inch rainfall is sufficient to 

 ensure payable wheat-growing, the map shows that it 

 can safely be done practically as far west as long. 146°, 

 and even further in the south ; but, generally speaking, 

 over the country further to the westward, embracing an 

 area of some 122,000 square miles, the rainfall does not 

 reach 15 inches, and is under 10 inches over an area of 

 about 45,000 square miles in the extreme west of the 

 colony. Mr. Hunt points out that the most remarkable 

 feature of the map is the comparatively light rainfall in 

 the district extending from Delegate, in the south, to 

 Yass, about 2° to the northward, owing to the condensa- 

 tion of moisture by the ranges of mountains by which it 

 is enclosed. 



Dr. H. Fritsche, emeritus director of the Pekin 

 Observatory, in a recent work (" Die saecularen Aender- 

 ungen der Erdmagnetischen Elemente," Riga, 1910) makes 

 an attempt, to which boldness at least must be conceded, 

 to extend our knowledge of terrestrial magnetism lo epochs 

 prior to direct observation. He starts with the assump- 

 tion that during the last several thousand years there have 

 been no outstandingly large changes in the earth's 

 inagnetism — a hypothesis for which much may be said 

 in spite of the deductions drawn by Folgheraiter from the 

 magnetism of Etruscan vases — and that such changes as 

 have occurred can be represented by periodic terms. For 

 these periods he assumes 500, 700, and 900 years, but his 

 reasons for this choice of periods are rather obscure. He 

 attacks the problem by taking as his knowns the values 

 he has calculated from observations for the Gaussian 

 coefficients for the epochs 1575, 1675, 1811, and 1892. 

 Regarding the Gaussian coefficients as expressed by- 

 periodic terms with unknown coefficients, he determines 

 the coefficients by reference to the four epochs just men- 

 tioned. He thus obtains general expressions from which 

 Gaussian constants are derivable for any given epoch, and 

 he makes use of these for the construction of isogonal 

 charts for the epochs 1200, 1300, 1400, and 1500 a.d. 

 Tables are given for the values of the Gaussian constants 

 extending back to 2700 B.C. Dr. Fritsche's work must 

 have entailed an enormous, amount of onerous calculation, 

 but it must be regarded as of an exceptionally speculative 

 character. 



KG. 2134, VOL. 84] 



In a communication made to the Institution of Electrical 

 Engineers in .'\pril last, which appears in the August 

 number of the Journal of the institution, Mr. W. P. Digby 

 directs attention to the advantages to engineers of tests 

 of the electrical conductivity of the water with which 

 they have to deal. He shows how, with a simplified 

 conductivity tube and a form of " megger " with its scale 

 graduated to give conductivity directly, an engineer may 

 detect immediately a change in the nature of the feed- 

 water for a boiler, or the amount of priming, or the 

 development of a leak in the condensers, and may control 

 with much greater certainty water-softening or oil- 

 eliminating plants. It is only by actual work with the 

 apparatus under workshop conditions that its utility in 

 practice can be tested and established, and it seems well 

 worthy of a thorough trial by engineers. 



The Engineer for September 9 contains an illustrated 

 article on the new armoured concrete viaduct at Rotterdam. 

 This viaduct measures 1600 m. — very nearly a mile — in 

 length, and was commenced in 1904, and is composed 

 of many normal bays and bridges of various tvpes. Each 

 pier 'of a normal bay is composed of four columns support- 

 ing the four armoured concrete girders which go to make 

 up the arch. The lower faces of these girders are curved 

 or arched, while the upper faces are flat. The concrete 

 used was composed, for the most part, of 450 kilos, of 

 Portland cement to half a cubic metre of river sand and 

 one cubic metre of gravel, the sizes of the stones in which 

 varied between 5 mm. and 30 mm. in diameter. Under 

 test loads, a 20 m. arch was deflected 3-26 mm., or 1/6140 

 of the span. A 15 m. arch was deflected 1-57 mm., or 

 1/9550 of the span. Normal bays not resting on abut- 

 ments were deflected, as an average, i mm., or 1/9770 of 

 the span ; normal bays resting on abutments were only 

 deflected 0-6125 mm., or 1/12600 of the span. 



An article in Engineering for September 9 contains an 

 interesting discussion on the progress of aviation during 

 the past year. The progress on the more practical side 

 has been much more striking than in the records achieved. 

 The number of machines which will actually fly is 

 enormously greater, and they do so with much less un- 

 certainty. The greatest advance has been made in cross- 

 country flight, and this is of the utmost importance. While 

 flight may now be looked upon as a fair certainty when 

 the weather is really calm, such weather is rare, in this 

 country at all events. Hence the greatest interest 

 attaches to the progress of flight in a wind, and in this 

 direction the advance has been considerable. Cross- 

 country flights are now undertaken in quite strong winds. 

 The aeroplane has, in the last year, ceased to be a 

 mechanical curiosity, which could do little save make 

 exhibition flights in exceptional weather over a prepared 

 track, and has become a practical machine for progress 

 across country. We have therefore now got to the stage 

 when the aeroplane must be reckoned with as a machine 

 which is a practical factor in human life, and, if progress 

 is as rapid in the future as in the past, it will very soon 

 be a most serious factor. Even in its present state, a 

 machine which can travel seventy miles an hour, and fly 

 at such a height that hitting it would be extremely difficult, 

 must have its uses in war, and with increase in the lifting 

 power, speed, and radius of action, these uses must very 

 rapidly aligment. Its useful capabilities in time of peace 

 are less easy to foresee ; but that a machine which can 

 travel in any direction with the speed of an express train 

 is destined to have an important influence on civilised life 

 is obvious. 



