Intelligence and Miscellaneous Articles. 457 



carbonic oxide, a few minutes after it has been treated with sul- 

 phide of ammonium, shows only one absorption-band between the 

 spectrum-lines D and E. From this unalterability in the bands, the 

 presence of carbonic oxide in the blood may be recognized ; in the 

 case of animals which have been gradually poisoned by a small quan- 

 tity of carbonic oxide, the gas can in this manner be detected. 

 It is desirable in such cases greatly to dilute the blood Nume- 

 rous cases have shown that after animals have been poisoned with 

 carbonic oxide, recovery takes place in the open air if the poisoning 

 has not gone too far. And Pokrowsky has shown that in this recon- 

 valescence no carbonic oxide, but more carbonic acid than usual is 

 exhaled. Defibrinated blood gradually loses its carbonic oxide on 

 standing in the air; hence in forensic cases rapid investigation is 

 desirable : yet several days may elapse without any appreciable 

 diminution in the quantity of carbonic oxide. — Zeitschriftfur analyt. 

 Chemie, vol. iii. p. 439. 



RELATION OF THE WEIGHT OF A MAGNETIZING SPIRAL TO THE 

 MAGNETIZING FORCE. BY DR. MENZZER. 



If an electro-magnet is to be constructed, the current for which 

 is to be produced by a given battery, it is of practical importance to 

 consider, first, what thickness and length of wire must be chosen for 

 the coil, and what combination must be once for all taken in order 

 to obtain the most powerful electro-magnet for the given cost. It 

 is assumed that the maximum of intensity is in all cases obtained 

 when the essential resistance, or that offered by the battery, is equal 

 to the external resistance in the interpolar, i. e. in this case the mag- 

 netizing coil. 



The author gives an investigation in a special case, from which he 

 arrives at the result that " the magnetizing powers of two coils which 

 give the maximum of intensity are as the square roots of their weights; 

 and he then states the question in a general manner as follows : — 



If e is the electromotive force of one cell, t the number of cells 

 which are united in one element, and 5 the number of such elements, 

 then st=n is the number of available cells ; if, moreover, X is the 

 internal resistance of one cell, m the length in metres of the copper 

 wire used for the coil, and d the diameter in millimetres of this wire, 

 the maximum intensity of the current is 



S=^^> (1) 



X , m v ' 



in which jmurt = |- (2) 



If, further, m' is the length in metres of the copper wire which is 

 used for one turn, then 



W=-, . . . (3) 



m 



Phil. Mag. S. 4. Vol. 30. No. 205. Dec. 1865. 2 H 



