4i8 



NATURE 



\Scpt, 24, 1874 



METEOROLOGY IN MAURITIUS 

 Results of Metcerological Obse>~vations taken in 1872 at 

 Mauntius ; Monthly Notices of the Meteorological 

 Society of Mauritius^ 1873 ; pp. 23 to 53. 



THE work of meteorological observation and discus- 

 sion at this important station continues, as shown 

 by these papers, to be prosecuted under Mr. Mel- 

 drum's direction with marked energy and success. 

 The observations at the observatory, which are made 

 live times daily, embrace atmospheric pressure, tem- 

 perature, humidity, cloud, rainfall, wind, thunder, light- 

 ning, and meteors, of which the " Results " present us 

 with a full and carefully prepared summary. We observe 

 with much satisfaction that a barograph is in operation at 

 this important observatory, and very earnestly hope that 

 future annual publications will give meteorologists what is 

 greatly desiderated, viz., the data for the determination of 

 the hourly barometric fluctuations of that region. It is 

 stated that the monthly means of the dry and wet bulb 

 thermometers have been derived from the observations at 

 6 and 9\ a.m. and 3.^ and 95 p.m. ; but those of the baro- 

 meter from the observations at ()\ A.M., 3]; P.M., and 93 P.M. 

 The formula employed in each case should in future be ex- 

 plicitly stated. We infer from an examination of the table 

 that the barometric means are derived from the formula 



"- "*" 32 'T 9'i . |3u{ ^g regards the thermometers, we 



4 

 have no means of knowing how the observations at the 

 four hours were combined in deducing the mean tempera- 

 ture, since the means ot temperature at these hours are 

 not printed. Considering the hours at which the observa- 

 tions are made, the best formula for the mean tempera- 

 ture would be %Lj_?-_T_^-_"'" :. But the most satis- 



4 

 factory course would be to give the averages at the 

 observed hours, leaving it to each to deduce from these 

 the approximate mean temperatures. In all published 

 annual results the simple averages of actual observations 

 ought to be gii-en, and these should in no case be made 

 to give way to averages hypothetically deduced. 



The rainfall has long occupied the attention of the 

 Mauritius meteorologists, and a table is given showing 

 the results of the rainfall at thirty-five stations. The 

 annual amounts vary greatly, from an annual average of 

 33 in. at Gros Cailloux to 146 in. at Cluny. The impor- 

 tant bearing of the rainfall on the products and health of 

 the island has been ably pointed out by Mr. Meldrum. 

 It is much to be desired that this very energetic society 

 should establish stations at suitable points over the island, 

 at which observations of pressure, temperature, wind, &c., 

 would be made. The position of the island, its peculiar 

 physical configuration, and variety of vegetable covering, 

 afford remarkable facilities for the investigation of not a 

 few meteorological problems, such as the influence of 

 forests on climate, and the daily march and phases of 

 the pressure, temperature, and humidity of the air as 

 influenced by height, exposure, and the character of the 

 vegetation in the immediate neighbourhood of the instru- 

 ment. 



The paper drawn up by Mr. Meldrum for the Vienna 

 Meteorological Congress regarding the practicability and 

 utility of storm warnings is of considerable value, the 



subject having long received full and able investigation at 

 Mr. Meldrum's hands, and the correctness of his deduc- 

 tions been abundantly tested by the success attending 

 the warnings issued by him. The chief, and indeed only 

 difficulty, in the way of the complete success of the 

 system of warnings at Mauritius is the uncertainty as to 

 when and where an advancing cyclone may recurve. 



But the most valuable article in these papers is the one 

 by Mr. Meldrum " On a rainfall periodicity corresponding 

 with the sunspot periodicity." The article is a fine in- 

 stance of a broad and comprehensive discussion of the 

 question dealt with through its details, and of an ex- 

 treme caution in constant exercise in drawing the con- 

 clusions. The result arrived at is this : — Whether we 

 take the annual rainfall over the largest possible portion 

 of the globe for short periods, or over a smaller portion 

 for a longer period, we arrive at the same result, viz., an 

 increase of rain at or^near the epochs of maximum sun- 

 spot area, and a decrease of rain at or near the epochs of 

 minimum sun-spot area. The exceptions are few and 

 trifling, being only such as might be expected in this as in 

 other questions of physical research, and they all gradually 

 and inevitably disappear from the results as the inquiry 

 is made to cover more extended portions of the earth's 

 surface and a longer interval of time. 



Much interest attaches to the prosecution of the inquiry 

 regarding the relations of solar and atmospheric changes 

 into other branches of meteorology, such as the pressure, 

 temperature, humidity, electricity, and motions of the air. 

 Does the temperature fluctuate with the sun-spot period ? 

 and if so, is the increase and decrease uniform and simul-' 

 taneous over the globe, or do the warm and cold periods 

 differ widely in different regions? How is the distribu- 

 tion of atmospheric pressure affected .' Are the inequalities 

 intensified or reduced, or does the difference find expres- 

 sion chiefly in a greater or less disturbance of the atmo- 

 sphere, resulting in an increase or decrease of the daily 

 fluctuation as measured by the observed differences in 

 the readings made, say at 9 A.M. from day to day? In 

 the further development of " the meteorology of the 

 future," these are some of the more important questions 

 that will be first inquired into. 



OUR BOOK SHELF 



A Manual of Metallurgy. By W. H. Greenwood, 

 F.C.S., Associate of the Royal .School of Mine;. 

 (London and Glasgow : W. Collins, Sons, and Co., 

 1874.) 



The author states that the work is " primarily designed " 

 for the use of students preparing for the advanced stage 

 of the examinations of the Science and Art Department 

 This, the first volume, contains 250 pages, of which 15a 

 are devoted to iron and steel. And it may be observed 

 that as there is an excellent treatise on the Metallui-gy of 

 Iron, by Baucrmann, in Weale's Series, this part is less 

 needed by students than the second, in which the meta'-. 

 lurgy of copper, lead, zinc, silver, gold, mercury, nickel, 

 cobalt and aluminium, will be described. 



Mr. Gr<;enwood has availed himself of his notes of Dr. 

 Percy's lectures at the Royal School of Mines, and has 

 spared no pains in gathering materials for the work from 

 original memoirs, as well as from the few well-known 

 French and German metallurgical «orks. The chapters 

 on fuel and fire-clays are necessarily brief ; but those. 



