NA TURE 



[May 5, 1904 



to four or five significant figures, and in consequence 

 expects to get greater credit than liis more indolent neigh- 

 bour who has been content with two or three significant 

 figures. Instances might be multiplied ; they constitute the 

 daily purgatory of every teacher. .Something surely is to 

 be said for a method which avoids these absurdities. 



Analytical methods have so dominated the elementary 

 text-book that many boys have the idea that statics is 

 practically useless. They have no notion, for instance, that 

 graphic statics lies at the foundation of bridge construction. 

 Besides, in how many questions in the elementary text- 

 book is the principle involved wholly obscured, because 

 a trigonometrical conundrum is required and not an appli- 

 cation of the conditions of equilibrium to give the unknown 

 forces? In a popular text-book one-third of the questions 

 at the end of one of the chapters are of this character. 

 Is it to be wondered at that the average boy gets the idea 

 that mechanics is a subtle epilogue to trigonometry? 



Each question treated graphically should be regarded in 

 the light of an experiment, in which the student should 

 get the best result available with the means at his disposal. 

 In any actual problem the daXa themselves are nofcorrectly 

 known, and the qtiaesita are therefore subject to all sorts 

 of cumulative errors. This he quickly finds out by com- 

 paring his result with that of his neighbour, and he readilv 

 g-ets a notion of the degree of accuracy that he himself 

 with pencil and ruler is capable of. 



-Mr. Larden writes : — " a student well trained in 

 analytical methods can always pick up graphical methods 

 rapidly when he needs them for special work." But will 

 he do so? The engineer is not trained in analysis and 

 allowed to adopt a graphical method when a specific 

 problem arises. My experience is that the student, who 

 has mastered analytical methods, is apt to consider graphical 

 work as drudgery, and when called upon to solve a question 

 graphically does not treat it with sufficient respect, and 

 gets an indifferent result. A certain amount of finesse and 

 judgment in choice of scale and of position of the initial 

 force or load is required " to fit the diagram on to a given 

 sheet of paper." This can be acquired only by practice. 



Unfortunately it is too true that " graphical work con- 

 sumes an amount of time that seems out of proportion to 

 the mental training and knowledge of principles gained," 

 but only when applied to too many similar questions. This, 

 however, is misusing, not using the method. 



I believe the best results will be obtained when the two 

 methods are used side by side. They are strictly comple- 

 mentary, and the merits of each supplv the deficiencies of 

 the other. ^ ' R. M. Milne. 



R.M. .\cademv, Woolwich. 



Asset and the Solar Eclipse of October 29, 878. 

 I'ndek the date dccclxxix, Asser, in his " Life of King 

 Alfred," gives the following entry: — " Eodem anno 

 ecHpsis solis inter nonam ct vesperam, sed proprius ad 

 nonam, facta est." The oldest manuscript of the Anglo- 

 Saxon Chronicle also notes an eclipse in 879, but it cannot 

 be doubted that in each case the reference is to the eclipse 

 of October 29, 878, which was total in South Wales and 

 southern England. Particulars of the eclipse are given by 

 Mr. Maguire in the Notices of the Astronomical Society, 

 vols, xlv., 400, and xlvi., 26. The sun rose totally eclipsed 

 in 73° N. and 42° 8' W. at about 9.53 local time, and the 

 central line of the eclipse, after passing near Dublin, 

 Aberystwith, Dover and Fulda, went off the earth at sun- 

 set about 130 miles south of Moscow at 4.20 local time ; 

 St. David's, Winchester and London were within the limits 

 of totality. With regard to the hour of the eclipse, it is 

 needful to consider not only mean time and apparent time, 

 but also natural time, which was the kind of time then 

 in use, according; to which the period between sunrise and 

 sunset was conceived to be divided into twelve hours, which 

 were, of course, much shorter in winter than in summer. 

 As the sun rose at London on the day of the eclipse about 

 7.20, the natural hour would have contained only about 

 47 minutes of mean time. Mr. Maguire gives the middle 

 of the eclipse at St. David's about 1.12, and at London 

 about i.iS mean time, and subtracting the equation of 

 time, about 15 minutes, w'e have 12.57 ^tid 1.3 for the 

 apparent time as shown by a sundial ; correcting for natural 

 NO. 1 80 1, VOL. 70] 



time, we obtain 1.13 for St. David's and 1.20 for London. 

 Finally, making allowance for the difference of longitude, 

 we see that totality occurred at St. David's at 12.46, and 

 at London at 1.20, according to local time as shown by a 

 waterclock, or some other time-keeper, properly regulated 

 to mark the natural hours. We now have to consider what 

 Asser meant by Nonam and Vesperafn. Those who have 

 written about the passage have taken Nonam to be identical 

 with Nonam Horam, but probably they have not been right 

 in doing so. It is shown in the " Dictionary of Christian 

 Antiquities " (i. 793) that the day and night were divided 

 into four equal parts, and that each quarter of the day 

 was named after the last hour in it. " None embraces the 

 seventh, eighth and ninth hours ; and the last called 

 Duodecima contains the tenth, eleventh and twelfth, ending 

 at Sunset." Asser, however, evidently uses Vespcra for 

 Duodecima. Nona is, in fact, noon, the point when the 

 sun is on the meridian, the beginning of the seventh hour, 

 and Vespera is the point half-way between noon and sunset, 

 in this case 2.20 mean time and 3.0 natural time. Thus 

 what Asser says is this, that the eclipse was total at a point 

 of time between noon and 1.30 natural time, and we see 

 that the statement is true for any point in England or 

 Wales. If we could be sure that the sentence about the 

 hour of the eclipse was written by Asser of St. David's, it 

 would be a very strong argument, indeed, for the genuine- 

 ness of the book which is called by his name, for it fixes 

 the moment of the eclipse correctly to within seventy minutes 

 of mean time for any place at which it is possible that the 

 book could have been written. C. S. T.avlor. 



Banwell Vicarage, April 23. 



" Abdominal Ribs " in Lacertilia. 



It is usually stated in text-books that among living 

 reptiles only the Crocodilia and Hatteria are furnished with 

 abdominal ribs or parasternum : that is, of course, in the 

 condition of thin pieces of bone lying between the ventral 

 muscles and underlying the true ribs, for no one doubts that 

 the plastron of the Chelonia is the satne structure exagger- 

 ated. There has been some little confusion between the 

 abdominal ribs and the ventral moieties of the true ribs 

 in Lacertilia, which is cleared up by Dr. Gadow in his 

 contribution to the " Cambridge Natural History." Dr. 

 Gadow correctly observes of the geckos that they possess 

 very long and slender post-thoracic ribs, " which meet each 

 other in the middle line, in this case bearing an extra- 

 ordinary resemblance to the so-called ' abdominal ribs ' of 

 other Reptiles." The statements as to "abdominal ribs" 

 made by M. Boulenger in his catalogue of the lizards in 

 the British Museum appear to me to refer to true ribs. 

 Of the Scincidas, he remarks that ossified abdominal ribs 

 are absent." Curiously enough, it is precisely in this group 

 that I find a parasternum. In Tiliqua scincoides the ventral 

 musculature is divided by the usual tendinous septa into 

 successive " myotomes," the tendinous intervals being dis- 

 tinctly ossified : there are several pairs of these bonelets 

 which seem to be exactly like those of Hatteria, with which 

 I have compared them. That they are not the ventral 

 moieties of the true ribs is shown by the fact that they 

 overlap the latter, the two series of structures lying at a 

 different plane in the musculature. I intend to make a 

 more detailed communication to the Zoological Society upon 

 this subject immediately. Fr.\nk E. Beddard. 



Inheritance of Acquired Characters. 



Recording the " non-inheritance of acquired characters," 

 the following is interesting : — 



I was recently visiting a sugar plantation near Ottawa, 

 Natal, and there was shown four fox terrier pups about a 

 fortnight or three weeks old, two of which had been born 

 with quite short tails, and one with a tail shorter than 

 the normal. The fourth pup had a full-length tail. The 

 mother was an ordinary fox terrier with cut tail. When 

 the circumstance of these dogs being born with short tails 

 was first mentioned to me I refused to believe it ; but ex- 

 amination showed that the short tails were really naturally 

 short tails and not tails that had been cut, that is to say, 

 the short tails had at their ends the usual tapering vertebrje 

 of a normal dog's tail, and, of course, at this age it was 

 easv to see that the tails had not been cut or bitten off. 



Cape Town, April 7. D. E. Hutchins. 



