368 



NATURE 



[A/ar. 7, 1872 



whilst the pearly cones existed in the solar atmosphere 

 and constituted a true solar corona. 



My long delay in making this communication to the 

 scientific world will be excused, I trust, in view of the im- 

 perative demands made upon my time during the two 

 years that have elapsed since the Eclipse of 1869. I shall 

 be deeply interested to learn whether the phenomena seen 

 by myself may not be repeated on some other occasion 

 and be studied by more experienced observers. 



I may add that I had hastily provided myself with a 

 Nicol's prism in hopes of making at least some trial of the 

 nature of the coronal light ; but the rude apparatus did 

 not work satisfactorily, and I confined myself to details of 

 structure ; indeed, in my earnest gaze upon the novel 

 phenomena I quite forgot the polarising apparatus. 



Cleveland Abce 



Office of the Chief Signal Officer, U.S. Army, 

 Washington, Feb. 6, 1872 



EARTH-CURRENTS AND THE AURORA BO- 

 REALIS OF FEBRUARY 4, 1872 



TT is unfortunate that more accurate observations of the 

 -'• electrical phenomena accompanying auroral displays 

 cannot be made upon the telegraph wires of this country. 

 The truth is, public business cannot be made to suffer for 

 scientific investigation, and at such moments the disturb- 

 ance of the wires makes it more than ever imperative that 

 delays should not occur. The whole efforts of the staff 

 are directed to maintain the communications intact, hence 

 the observations made on February 4 are not very nume- 

 rous, though they are sufficiently interesting to deserve 

 record. 



At Portsmouth twenty-six observations were made of 

 the direction and strength of the earth-currents on a wire 

 extending from Portsmouth to London, via the London 

 and South- Western Railway — a length of 74 miles, giving 

 a resistance of 995 ohms. These were as follows : — 





40° ; fNo observa- 



— ') tionsmade 



o I between 



41 i6.4i&7.35. 

 68 



/No observa- 

 I tions made 

 ( between 

 ,j8.30 & 9.0 

 (p.m. 



P means Positive from London to Portsmouth. 



The officer who made these observations writes : — 

 " Strong deflections arising from earth currents were ob- 

 served on all circuits except the local ones. The duration 

 of the currents changed from north to south at intervals 

 of a few minutes, and varied in strength from i°to68°. 

 The strength of the current was proportionate to the 

 length of the wire. Thus Chichester circuit (a short one) 

 was affected less than the Guildford, and the latter less 

 than the London circuits. The working was maintained 

 to London with comparative ease by looping two circuits 

 together at each end." The latter method is that usually 

 adopted to overcome the disturbance due to earth currents, 

 but of course it is only applicable in places where there 

 are two wires or more. 



Another officer at the Waterloo Station, London, ob- 

 served the deflections gradually appear on every needle 

 circuit, of which many concentrate at that station. They 

 commenced about 2 p.m., and from that period to 8 VM. 

 they had all alike been more or less disturbed. It was 

 noticed that the needles moved over gradually, not by a 

 continuous motion, but by jerks, resembling that of the 

 minute hand of a large clock. This has, however, been 

 proved to be due to the friction of the pivots, and not to 

 any pulsations in the currents. 



The currents were always most apparent, and first no- 

 ticeable on the longest lines, and as the lengths of the 

 circuits terminating at Waterloo are very variable, this 

 gradual appearance was very interesting. Lines running 

 south-west and west appear to have been most affected. 



All the wires in the Channel Islands were also very 

 much disturbed. In fact Jersey was broken down to 

 England for three hours, owing to the fact of there only 

 being one cable. The section most affected was that 

 between England and Guernsey. It was also noted that 

 the wires in France were very much influenced. 



The records from abroad show that, as in previous e ases 

 of storms of this character, the effect has been simultaneous 

 all over the globe. The French Atlantic cable was 

 seriously affected ; the strength of the current was at one 

 time equal to 90 Daniell cells. It was at times im- 

 possible to read even with condensers in circuit. The 

 American lines were also disturbed in the East, West, 

 and North, but not in the South. 



It is much to be regretted that simultaneous observa- 

 tions cannot be made in various parts of the globe, detail- 

 ing, in comprehensible units of measurement, the direction 

 and strength of these currents, as w'ell as the exact time 

 of their appearance and disappearance. We might then 

 arrive at some knowledge of their cause. 



Southampton, Feb. 24 W. H. Preece 



THE DARMSTADT POLYTECHNIC SCHOOL 



'X'HE following epitome of the programine of the 

 ■'• " Grand Ducal Hessian Polytechnic School of 

 Darmstadt" may interest the readers of Nature as a 

 further illustration of the facilities offered in Germany 

 for technical training of the highest and most practical 

 kind. 



The object of the school is stated to be a thorough 

 scientific, as well as artistic, education, for all technical 

 pursuits, assisted by appropriate practical exercises. The 

 institution affords special facilities for the education of 

 architects, engineers, mechanical and chemical technicists, 

 manufacturers, craftsmen, and agriculturists. The insti- 

 tution is divided into the following sections : — (i) the 

 Lower School ; (2) the School of Architecture ; (3) of 

 Engineering ; (4) of Machinery ; (5) of Technical 

 Chemistry ; and (6) of Agriculture. 



The Lower School aims at giving a general instruction 

 in mathematics, natural science, and design, as a founda- 

 tion for the special pursuits taken up afterwards. For 

 admission into the school it is necessary that the student 

 shall be sixteen years of age, and have received such an 

 education as would be afforded by the highest class of 

 a " Kealschule," or the third course of a " Gymnasium," 

 with the exception of the dead languages. This implies 

 a knowledge of algebra, as far as equations of the 

 second order, an acquaintance with logarithms, with plain 

 geometry, and the elements of solid geometry, practice in 

 German style, a knowledge of the outlines of history, and 

 some practice in linear and free-hand drawing. 



Examinations are held in the lower school at the end of 

 each half-year, in the other divisions at the end of each 

 year ; a diploma is only given if the student gives satis- 

 factory evidence of having completely mastered one of 

 the branches of technical study in which special instruc- 



