Ml'. J. Joule on the Magnetism of Iron Bars. 77 



Linnseus is sadly wanted to correct this pernicious habit, both at 

 home and abroad. 



The group now under consideration exhibits a great tendency to 

 variation of form, some of the combinations (especially in the case of 

 MargtnuUna) being as complicated and various as a Chinese puzzle. 

 It is, I believe, undeniable, that the variability of form is in an in- 

 verse ratio to the development of animals in the scale of Nature. 



Having examined thousands (I may say myriads) of these elegant 

 organisms, I am induced to suggest the following arrangement : — 



1. Lagena (Walker) and Entosolenia (Williamson). 



2. Nodosaria and Marginulina (D'Orb.), &c. 



3. Vorticialis (D'Orb.), Rotalia (Lam.), Lobatida (Flem.), Glohi- 

 gerina (D'Orb.), &c. 



4. Textuluria (Defrance), Uvigerina (D'Orb.), &c. 



5. Miliola (Lam.), Biloculina (D'Orb.), &c. 



This division must, however, be modified by a more extended and 

 cosmopolitan view of the subject, as I only profess to treat of the 

 British species. To illustrate MacLeay's theory of a quinary and 

 circular arrangement, the case may be put thus. 



Lagenadse. 



■2!. 



V .^^ 



<^ 



The first family is connected by the typical genus Lagena with 

 the second, and by EntosoUna with the fifth ; the second is united 

 with the third through Marginulina ; the third with the fourth 

 through Globigerina ; and the fourth with the last through Uvige- 

 rina. 



Whether these singular and little-known animals are Rhizopodes, 

 or belong to the Amoeba, remains yet to be satisfactorily made out. 



London, June 18, 1855. 



" Preliminary Research on the Magnetism develoj^ed in Iron Bars 

 by Electrical Currents." By J. P. Joule, F.R.S. 



The author had, many years ago, found that the magnetism deve- 

 loped by electro-magnetic coils in bars of upward ^rd of an inch 

 diameter, was nearly proportional to the strength of the current and 

 the length of the wire, any alteration, within certain limits, of the 

 diameter of a bar being attended with only trifling effects, so long 

 a.s the point of saturation was not nearly approached. The Russian 

 philosophers Lenz and Jacobi had, however, stated that the mag- 

 netism developed was, ccelcris paribus, proportional to the diameter 

 of the bar. The discrepancy between the above results is considered 



