y^ily I, 1 875 J 



NATURE 



167 



South American Earthquakes 



On the 1 8th May, that is, the same day that, if the telegraphic 

 news be correct, the cities of Cucuta, Santiago, and others 

 were destroyed by an earthquake, a distinct and prolonged 

 shock, preceded and accompanied by a loud rumbling noise, 

 awoke the greater number of the inhabitants of this place, about 

 a quarter of an hour before midnight. The direction of the 

 phenomenon was thought by some who heard and felt it to 

 be from east to west ; but this opinion was, I have reason to 

 believe, inaccurate. 



Not knowing as yet the exact time at which the Columbian 

 disaster took place, I am unable to calculate the rate at which 

 the shock, connected with, one can hardly doubt, the great 

 earthquake above alluded to, may have travelled the long dis- 

 tance that separates St. Thomas from Cucuta. Fuller details 

 may subsequently, I hope, help to elucidate the matter. 



It is worthy of note that whereas before the 1 8th May an 

 unusually long period had elapsed during which no subterraneous 

 vibrations had been felt in this island, there have occurred since 

 that date several slight shocks at various hours of the day and 

 night, with a frequency above the average. 



St. Thomas, West Indies W. G, Palgrave 



Glacier and other Ice 



The reviewer of CroU's " Climate and Time" in Nature of 

 the 24th June (p. 144) says : *' What is there in this (Mr. CroU's) 

 theory to distinguish a glacier from a common piece of ice ? 

 which on this principle ought . to flatten out and not retain its 

 shape as it does." 



I believe that, independently of any theory of the cause of 

 glacier motion, there is no physical difference whatever between 

 glacier and other ice. The greater mobility of a glacier is 

 merely due to its greater size and weight ; just as water in a river- 

 bed flows with very little friction, under a pressure that would 

 not make it flow at all in a capillary tube. The plasticity of ice 

 may however be shown on a small scale. I have read some- 

 where that a slab of ice supported only on its two ends will 

 gradually bend down in the middle : and I have seen Prof. James 

 Thomson at the Belfast Museum illustrate a lecture by moulding 

 a ^e.\i lumps of ice by pressure into the shape of a cup. 



I am not writing in defence of Mr. CroU's theory of glacier 

 motion. I believe the best explanation of those physical 

 properties of ice on which glacier-motion depends is that given 

 by Prof. James Thomson. I know Mr. CroU's theory only 

 from your review, and I do not know how far it agrees with 

 I'rof. Thomson's. Joseph John Murphy 



' )ld Forge, Dunmurry, Co. Antrim, June 26 



The House-fly 



I AM disappointed to find that no one has answered 

 "Harrovian's" query in vol. xii. p. 126, as to the mortality 

 amongst the house-fly, and the yellow powder which covered 

 the carcase. I have noticed myself that house-flies often die 

 in numerous company. I had an idea that it was owing to 

 the temperature falling to its benumbing point, until I found the 

 same thing happening while the thermometer was particularly 

 high. Then I thought that all these dead flies might belong to 

 the same brood, and having lived under almost exactly the same 

 circumstances, their threads of life were spun out at almost 

 exactly the same time. This new theory, again, did not stand 

 examination well under the microscope. But the result of my 

 experiment differed slightly from that of " Harrovian." At least 

 I find I entered in my notes, "the body covered with white 

 eruption, apparently a disease of the skin." 



Denstone College, Uttoxeter D. Edwardes 



OUR ASTRONOMICAL COLUMN 

 An Ancient " Uranometria." — We have received a 

 very interesting work, published by Dr. Schjcllerup, of 

 the Observatory of Copenhagen, under the auspices of 

 the Imperial Academy of Sciences of St. Petersburg. It 

 contains a description of the constellations, with the star 

 magnitudes, composed in the middle of the tenth century 

 by the Persian astronomer, Abd-al- Rahman al-Sijfi, and 

 is a literal translation of two Arabic manuscripts preserved 



in the Royal and Imperial libraries of Copenhagen and 

 St. Petersburg. A more particular account of the valu- 

 able addition which Dr. Schjellerup has made to the 

 literature of astronomy will be given in this colun»n next 

 week. Meanwhile, we may just note one curious state- 

 ment made by the Persian astronomer with reference to 

 the well-known variable star Algol, viz., that at the time 

 of his observations the star was reddish — a characteristic 

 applied also to Antares, Aldebaran, a Hydrae, and a few 

 other stars, which are also reddish in our own day ; but 

 at present there is no tinge of colour about Algol, which 

 may be fairly described as a white star, and if there be 

 one of its class more than another in which the periodical 

 fluctuation of light can with much appearance of proba- 

 bility be attributed to the intervention of a revolving 

 attendant, passing regularly in our line of sight, it is to 

 this star that we might point in illustration. Its former 

 ruddy light, however, rather necessitates a different ex- 

 planation, and one which, notwithstanding the compara- 

 tive regularity of its changes, may perhaps assimilate it 

 to the more numerous class of variable stars. 



The "Black Saturday" Eclipse, 1598, March 7. 

 — This eclipse, which was visible in its total phase in 

 Scotland, like that of 1652, April 8, noticed in this column 

 last week, was remembered long afterwards in that country, 

 the day of its occurrence being called " Black Saturday." 

 The elements were very approximately as follows : — 



Conjunction in R, A. 1598, March 6, at 23h. im. 38s. G.M.T. 



The semi-diameter of the belt of totality appears to have 

 been about forty-five miles only. This belt included 

 Edinburgh, where the total eclipse commenced about 

 loh. 15m. 36s. A.M. on March 7, local mean time, and 

 continued im. 29s. with the sun at an altitude of 26°. At 

 Douglas, Isle of Man, the eclipse was also total for about 

 the same interval, the sun disappearing at loh. 6m. 43s. 

 A.M. local time according to the above elements. 



The date for this eclipse is given for new style, as was 

 also that for the eclipse of 1652. 



While referring to this subject we may mention that 

 Dr. Celoria, of the Observatory of Milan, has calculated 

 the circumstances of the total solar eclipse of 1239, June 3, 

 from the tables of Hansen— with Leverrier for sun. Prof. 

 Schiaparelli had collected together a large number of 

 notices of the totality of this eclipse in its passage across 

 Italy, his authorities being chiefly found in the great work 

 of Muratori. It appears to have been total (if we may 

 assume totality from the visibility of stars and the night- 

 like appearance of nature) at Monpellieri, Mirabeau 

 (where Zach found an inscription referring to the pheno- 

 menon), Digne, Ales^ndria, Genoa, Piacenza, Parma, 

 Lucca, Modena, Florence, Siena, Arezzo, Este, Ravenna, 

 Lesina on the Adriatic, &c. ; but Hansen's tables, accord- 



