514 Sir G. C. Haughtoii 07i the Common Nature of 



with a magnet; while the second specimen, which was com- 

 paratively I'ecent, as was evident from its fine colour, gave 90° 

 with the magnetic needle ; and the probable cause ot this dif- 

 ference will be shortly seen, when 1 ipeak of the results ob- 

 tained with a needle made out of a part of this very piece of 

 ivory. Glue exhibits phasnomena of a very interesting cha- 

 racter. Its affinity for the magnet was only 29°, after the 

 most painful efforts were repeatedly made to push it further, 

 but on being left in contact with the bar-magnet for some 

 hours, it instantly attached itself at 38°. Its affinity for the 

 iron was 90° + , and it exhibited the same amount of attraction 

 for pure gold, platinum, cadmiuni, tin, zinc and arsenic, 

 which were all the metals it was tested with. But I have 

 some doubts about all the high measurements, as I fear that 

 the dampness of the weather may have influenced the results, 

 though the different specimens appeared perfectly hard. 



Ilh Class. 



Deal wood with M 30° ; T 30° ; B 90°, f. 



Box wood with T 15°. 



Rose wood with T 90°. 



Oak with I 90°, very difficult ; B 90°, f. 



Lignum vitse with M 33°; 118°; Cad. 22' ; T. 90°; L 90°. 



Cedar wood with M fliiled ; B 90°-F. 



Vegetable ivory with M 56'^; I 67°; G 18c. 90°; Cad. 90° + ; 



T 90°, very difficult. 

 Vegetable ivory (2nd specimen) with M failed: I 50°; P. G. 



90°, f. firm ; L 80°; Z 90°+ ; Cop. 90°+ ; Gl. 90°, f. strong. 

 Vegetable ivory (3rd specimen) with M failed ; I 70°. 

 Mahogany with B 90°, f.; Gl. 24°. 

 Lac (pure) with M 35°; P. G. 90°; G 18c. 74°; Cad. 90°; 



T 90° + ; L 90°; Cop. 65°; Gl. 90° f. 

 Sealing-wax (black) with M 25°; I Tailed; T 70°. 

 India rubber with M 80°; Cad. 90° + . 

 India rubber (botde) with P. G. 70"; B 90°+ ; Gl. £0°, f. 

 Resin with M 90° : T 90° X; Gl. 48°. 

 Gum with Gl. 90°+. 

 Macaroni with Gl. 40^ 

 Dry paste on paper with M failed ; Gl. 23°. 



The peculiarity connected with the attraction of lignum 

 vitae and vegetable ivory for the magnet and other substances 

 is remarkable. The lignum vitae was raised from 33° to 49° 

 by contact for a short time with a magnet, and the same pro- 

 cess raised it from 18° to 30° with iron, while with tin and 

 lead it had exhibited 90°, and only 22° are marked for cad- 



