347 



swarm had issued, and proceeded directly to the one which had just 

 settled, and instantly united with them. The author is led from 

 these and other facts to conclude that such unions of swarms are ge- 

 nerally, if not always, the result of previous concert and arrange- 

 ment. 



The author proceeds to mention some circumstances which induce 

 him to believe that sex is not given to the eggs of birds, or to the 

 spawn of fishes or insects, at any very early period of their growth. 

 Female ducks, kept apart from any male bird till the period of laying 

 eggs "approached, when a musk drake was put into company with 

 them, produced a numerous offspring, six out of seven of which 

 proved to be males. 



The mule fishes found in many rivers where the common trout 

 abounds, and where a solitary salmon is present, are uniformly of the 

 male sex ; hence the spawn must have been without sex at the time 

 it was deposited by the female. 



The author states that he has also met with analogous circum- 

 stances in the vegetable world, respecting the sexes of the blossoms 

 of monoecious plants. When the heat is excessive, compared with 

 the quantity of light which the plant receives, only male flowers ap- 

 pear ; but if the light be in excess, female flowers alone are pro- 

 duced. 



On the Laws of the Deviation of Magnetized Needles towards Iron. 

 By Samuel Hunter Christie, Esq. M.A. F.R.S. #c. Read June 5, 

 1828. [Phil. Trans. 1828, p. 325.] 



The author had pointed out, several years ago, the law of devi- 

 ation of a magnetized needle, (either freely suspended or constrained 

 to move in any particular plane,) from its natural position, by the in- 

 fluence of masses of iron in its vicinity. This law was founded on 

 the hypothesis that the iron attracted both the poles of the needle : 

 the position of which, resulting from this action, might be deter- 

 mined by that of an imaginary minute magnetic needle, freely sus- 

 pended by its centre of gravity, reduced to the plane of revolution. 

 The author had considered this law as fully established from its ac- 

 cordance with experiment ; but Mr. Barlow, in a paper which was 

 published in the last volume of the Philosophical Transactions, denies 

 that such an accordance exists, and infers, from the results of some 

 experiments which he made on horizontal needles, having their mag- 

 netism unequally distributed in their two branches, that the theory on 

 which the preceding law is founded is fallacious. In opposition to 

 the views of Mr. Barlow, the author contends that the phenomena 

 observed are precisely those which must result from the theory he 

 had himself adopted ; and that they tend in no way to support the 

 hypothesis of their being simply the effects of the magnetic power 

 which the iron receives by induction from the earth. 



The author was also led to suspect the accuracy of another con- 

 clusion which had been drawn by Mr. Barlow, namely, that the 



