1 G2 Progress of Foreign Science. 



the same way, the compound transversal magnetism, without 

 its extremities having a stronger magnetism than each of its 

 cross sections. These transversal-magnets with manifold po- 

 larities, have all the above enumerated properties of the single 

 transversal magnets, but their phenomena are still more in 

 unison with those of the electrical conjunctive wire; for, vnder 

 this manifold polarized magnet, the deviation of the needle is 

 the reverse of that above the magnet. 



In the following manner we may produce a section of a 

 manifold polarized transversal magnet in a larger rod, and 

 with a proportionally greater number of poles. We take a 

 ring of steel wire, from four to six inches diameter, and furnish 

 it with as many poles as we can apply to its circumference. 

 Lay the ring flat on a table, and apply to its outer edge the 

 two poles of a hcrse-shoe magnet, that are as near each other 

 as possible ; then remove the magnet and apply it in succession 

 all around, at distances equal to the width of its own poles. 

 In this way it is easy to induce on a steel ring, of about five 

 or six inches diameter, from twenty to thirty opposite poles. 



This steel ring which represents a section of the manifold 

 polarized transversal magnet, exhibits relatively to the greater 

 extension and smaller number of the existing magnetisms, 

 the phenomena which a section of the conjunctive-wire pre- 

 sents. In every part of it the magnetic needle with its north 

 end above it, stands to the right hand ; below it, to the left ; 

 and inversely. M. Prechtl thinks that these direct results 

 leave no further doubt concerning the magnetical condition of 

 the conjunctive wire. 



IX. Natural History. — It results from the researchesof 

 Baron Humboldt, that in all the temperate zone, the glumaceous 

 and composite plants, form together more than a fourth of the 

 phanerogamous, (plants with visible flowers, to distinguish them 

 from the cryptogamous.) The forms of organized beings are 

 found in mutual dependence. The unity of nature is such that 

 these forms have limited each other, according to constant and 

 immutable laws. When we know for a certain point of the 

 globe the number of species which a great family, (for example, 

 that of the glumaceous, composite, or leguminous,) presents, we 

 may estimate, with much probability both the total number 

 of the phanerogamous plants, and the number of species which 

 compose the other vegetable families. Thus by knowing, 

 under the temperate zone, the number of the cyperaceaa or com- 

 posite, we ma" guess that of the gramineous or leguminous. 

 These estimates shew us also in what tribes of vegetables, the 

 floras of a country are still incomplete. The geography of 

 plants may be considered as a part of terrestrial physics. 



On comparing the different systems of grouping in the two 



