•94 



NATURE 



\yan, 30, 1879 



constant difference between the average pressure of two 

 neighbouring regions which, though protracted, is not per- 

 manent, but disappears after a longer or shorter time. Mr. 

 Blanford largely inclines to trace the failure of the rains 

 to an unusually great expanse of snow covering the 

 viouthern slopes of the Himalayas, much of which fell 

 very late in the season, and which acted as a cooling agent, 

 bringing about an abnormal distribution of pressure, and 

 consequently of winds, temperature, and rainfall, con- 

 ditions which, once fairly established, went on reproducing 

 themselves so that cyclonic and anti-cyclonic areas of 

 an abnormal character gained a certain persistency over 

 those parts of India where the rainfall was deficient and 

 where it was in excess. Should future observations 

 confirm this hypothesis, the result will be one of the 

 most important yet arrived at in practical meteorology. 



The least satisfactory part of the report, perhaps, is 

 that referring to the relation of rainfall to the sun-spot 

 period, in which too much stress appears to be laid on 

 the results of data collected from a wide geographical 

 superficies, and too little stress upon data referring to 

 limited regions ; the data of which regions, it may be 

 added, require for their satisfactory discussion to be ex- 

 amined with reference to their seasonal as well as annual 

 variations during the sun-spot periods. 



The practical part of the "Indian Meteorologist's 

 Vade-Mecum " being part i of the work, is in many re- 

 spects a model-handbook for the observers for whose use 

 it is intended. The clearness with which the difficulties 

 attending the making of real observations of temperature 

 are apprehended is altogether admirable ; and the pro- 

 risions and precautions as regards instruments, hours, and 

 modes of observing actually taken are of such a nature as 

 likely to secure observations of a high quality, owing to an 

 increased intelligence, and efficiency on the part of the 

 observers who work in accordance with the principles and 

 instructions laid down for their guidance. 



Mr. Chambers' book is an elaborate and important 

 work on the Meteorology of the Bombay Presidency, 

 based on all the observations made in the Presidency 

 down to 1874. Its splendid porte-folio of eighty highly 

 finished maps and diagrams printed in colours, as well as 

 its excellent typography with 159 tables of results, many of 

 them being wholly or in part laborious and elaborate 

 analyses of the different data of observation, render the 

 work an edition de luxe. The contributions with which 

 this work enriches Indian meteorology are twofold, viz., 

 the results of the hourly observations made for many 

 years at Kurrachee, Deesa, Bombay, Poena, and Eel- 

 gaum ; and the monthly averages for numerous stations 

 throughout the Presidency, from which the temperature, 

 rainfall, and winds of this part of Asia are charted with a 

 fulness and consequent approximation to the truth not 

 hitherto attainable. The influence which the broad 

 physical features of the region, such as its lofty mountain 

 ranges, high plateaus, river valleys, and extensive sandy 

 deserts, has on the climatology of the Presidency is worked 

 out with great skill and ability. Still more able are the dis^ 

 cussions of the hourly observations of pressure, tempera- 

 ture, humidity, and cloud, made at the five chief stations, 

 together with many suggestive reflections on the results 

 developed, which will well repay the reader's best atten- 

 tion, even though he may sometimes not see his way to 

 agree with the opinions expressed. 



A healthy feature of Indian meteorology is the vigorous 

 manner in which the making of hourly observations is 

 pushed at many stations which have been admirably 

 chosen as respects the objects sought to be attained, and 

 the comparatively full and prompt discussions of the re- 

 sults which are published from time to time. Of the 

 problems handled in those discussions the most frequent 

 as well as the most important is that of the diurnal oscil- 

 lations of the barometer. To this very difiicult problem 

 Mr. J. Eliot, for example, makes a valuable contribution 



in a paper on two storms in Bengal during 1876, which 

 were accompanied with increased atmospheric pressure, 

 and the apparent reversal of the normal diurnal oscillation 

 of the barometer. This reversal was found to be accom- 

 panied with an instantaneous and complete change of wind 

 direction and a great fall of temperature, which, as they 

 occurred before the rain began to fall, proved that they 

 were not due merely to an inrush of a strong humid 

 current from the Bay of Bengal. The sudden chilling of 

 the air, accompanied as it was by an increase of pressure, 

 also proved that the changes were not due to the internal 

 action of a mass of air or to horizontal or surface currents 

 from the interior, which would have been warm cur- 

 rents, but that they were probably produced by the down- 

 rush of a cold upper current, a conclusion which will 

 doubtless receive further examination not only from its 

 bearing on barometric fluctuations but also on the theory 

 of storms. 



OUR BIG GUNS 

 ■\17'E may leave the explanation of the disaster on board 

 '» the T/nenderer ior t\iQ present to those who have 

 been appointed to inquire into the matter. But in the 

 mean time it will be well to consider what are the elements 

 of weakness, if any, in the construction of our big guns. 



The system of building up large guns by shrinking 

 coiled iron tubes over a central steel tube seems extremely 

 well adapted to prevent a latei'ai explosion ; for even 

 when the steel tube has had a longitudinal crack, the gun 

 has been frequently fired without any further evil conse- 

 quence. 



But our guns are manifestly deficient in longitudinal 

 strength, for the steel tube is the only tube continuous 

 from end to end. If, then, there should be any ring-crack 

 in the steel tube, there is little to prevent its separation 

 into two parts beyond the friction of the coiled tubes, and 

 the dove-tailing by which it is attempted to join the coiled 

 cylinders together. 



Now considerable longitudinal stress on the steel tube 

 must be caused every round by the rifling necessary to 

 give the shot its proper rotation, and occasionally, by a 

 jamming of the shot. Also every discharge of the gun 

 must cause a violent vibration in every part, and should 

 the junction of the i B coil with the C coil and breech- 

 piece work rather loose, this would be likely to cause a 

 ring-crack in the steel tube in that neighbourhood. 



When rapidly-exploding powder was used in the service 

 the guns were very properly rifled with an ittcreasing 

 twist with a view to remove every possible obstruction to 

 the initial motion of the shot. The increasing twist is 

 still in use notwithstanding all the efforts that have 

 been made to manufacture a powder that will burn 

 slowly, so as to make the propelling pressure on the 

 shot more nearly uniform. With a view to distri- 

 bute the work of giving rotation to the shot uni- 

 formly along the bore, the rifling should be calculated 

 to give a nearly constant pressure on the studs. Bist 

 this depends upon the law of explosion of the powder. 

 And this law is very variable, and very little understood. 

 Only we know this — that the more nearly the force pro- 

 pelling the shot becomes constant, the more nearly the 

 rifling approaches the uniform twist in order to obtain a 

 constant pressure on the studs. Now the objection to 

 the increasing twist is that it throws the chief part of the 

 work of giving rotation towards the muzzle, where the 

 gun is weakest. Also there is a difficulty in arranging 

 the studs on the shot, and it now appears that the 

 increasing twist allows the shot to slip forward when the 

 gun is depressed. It seems, therefore, desirable to 

 revert to the uniform twist of rifling now an improved 

 po^^der is used. 



But in order to give the gun additional strength in 

 direction of its length, it seems desirable that the steel 



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