3?^' Dr. Tyndall on the Laws of MnffneUsm. 



Tlie weights here appHed vary only within narrow limits. 

 Another series of experiments, commencing with 300 grammes 

 and ending with 900, follows. Xm. addition of 100 grajumes was 

 made at eveiy new determination. For the sake of convenience, 

 the weight is made the divisor ; and to avoid decimals, tan /8 is 

 multiplied by 10000 = ry. •i.iu.joai . , • ■ :- 



bolfiaim ! 

 Table II."' ' ^'""'^ 



gtan/3 

 W. ^. ""W"' 



\uv. .!,,': >/•. .300 - 6 35,::. ;;.: ^^ : 'A' 



400 9 15 it h);i(i<rr4!'Q7w ttrtTifja n ^.f'!it 



500 ' 11 30 ■ . .!^,v "4i06»n,!o-, .K/. (fv',1. 



600 13 30 4-00 



700 16 4-10 



800 17 53 4-04 



900 20 4-04 



-S'lo'^V.l fill.?' '■.» Iljli' !■ ._ .- I M ; !;i : 'I'l ii \ :l !-.!li'| '(:> -■, 



(.Another I s'ej'ies, m which 150 gi^n^^s ,^;gi^eijgnd^d after each 

 ejfpei;iiueftt,,i&,hQre iutroducct^^j gj^ f^ i,9jj„rrio(j doiriv. 



ii in j3nd)fn." W.i )!;,;,. li- /j..>i/?n() oJ ojundj JjpB'Ji gvodij baoyf'i 



9ilt iS/xnJs! Dfli^^oilloq fli JjAij}lSjm i; n\ ti^amBlgf* to i'l >fr>ii(l 

 fl9>Io"id Kfiv/ fifli™ 'irif hue yjimooi odJ J'iol a-ii/^ 



,xtiB§B Y.''-'^''^'i!w'oii^'^ '^^'^"'^ Ilarmw 9if;t ^oggnriJa 

 >" ■ 17 *o 4'iy [,„„,.r„ .,„„, 



-BvlBg inj;-iM "ifiri.) ^nojtf.JlDnfVdJ /Ino ior^^"?// eidJ xil .81 



h-irvj>dn 'S. I'. ■r't-3tflo(t(;;[j;l! ■•-. i-^trf'''-- --rift n.,[r: *rM! -rntira..'^ 



^JJsi'Talile Liwejohsferve that i^iis a coilsltant i^uantity>: and 



in the other tables we see that ' „ is constant. . ^ This leads us 



to the following law : — TJie mutual attraction of an electro-magnet 

 and a sphei-e of soft iron, when both are in contact, is directly pro- 

 portional to the strencjth of the magnet. 



12. The helix which surromided the core used by Lenz and 

 Jacobi was composed of two separate wires. The two ends of 

 one of these wires were connected MTith the })oles of the battery, 

 Avhile the ends of the other were connected with a galvanometer. 

 On sending a current through the former, an instantaneous 

 stream was induced in the latter, winch ran round the galvano- 

 meter, imparting in its passage a shock to the magnetic needle 

 of the instrument. Calling the extreme angle attained by the 

 needle in consequence of this shock 0, it is easy to prove 



