580 



In addition to the currents whose direction has been already noted, 

 42 cases occurred of currents which, for distinction sake, are called 

 Abnormal, and which were equally definite in character. They are 

 found in the S.E. and N.W. quadrants ; but the probable place in 

 these quadrants could not be determined with any approach to accu- 

 racy from the lack of other lines of telegraph immediately at com- 

 mand. Four diagrams are given in illustration of the normals and 

 abnormals. 



The author mentions that the South-Eastern Railway Company 

 have cordially entertained the proposition, to which he has previously 

 referred, of the Astronomer Royal ; and that he is now preparing to 

 erect wires for Mr. Airy, terminating respectively near Dartford and 

 Croydon, and which by combination will give an angle of 36 or 

 107, the former, however, being without the range of normal di- 

 rection. The consecutive observations to be made on these wires pro- 

 mise to be very instructive. The porcelain- ebonite insulator that 

 will be used is described ; a specimen is on the table. 



Among the 276 October-November observations, four cases oc- 

 curred which are exceptional and do not admit of similar discussion. 

 Subsequent observations may explain these. 



Next follows a survey of the N. and S. boundaries of a plane, the 

 mean dimensions of which are 56 miles X 20 miles, bounded on the N. 

 by the Thames, and on the S. by the Dover-Tonbridge line of railway. 

 This was accomplished by aid of the earth-plates at Ramsgate and 

 London, to the former of which access was had at Tonbridge, when 

 required, by means of a switch at Ashford Junction. A Table is given 

 of observations made during November and December, which show 

 that the plane of the current is at least 20 miles wide, and the di- 

 rection is consistent at either limit of the plane. 



Tonbridge being very nearly midway on a line joining London and 

 Hastings, gave the opportunity of making observations on the whole 

 or on either half of a same line of country. The results collected 

 in November and December are given in a Table, and show a confor- 

 mity in direction in the whole and in both halves, but a marked 

 excess in value in the London-Tonbridge as compared with the 

 Hastings-Tonbridge section. These differences are considered by 

 the author as probably due to the different geological conditions of 

 the country on either side of Tonbridge. Sections kindly furnished 



