270 Scientific Intelligence. 



suited in failure. I have finally mastered it. The same or a 

 similar form occurs among the infusoria from Greenport, Long 

 Island, which you sent me. The shells are beautifully cross 

 lined, much finer than in the N. Spencerii. You will find this 

 object worthy to head the list of tests." 



The form alluded to is a species of Grammatophora, possibly 

 referable as a variety to G. oceanica, Ehr., but which I propose 

 to name 6r. subtilissima, on account of its exceedingly minute 

 stria. It is abundant on our coast, and its markings are so 

 minute that with a glass which readily resolves the Navicula 

 Spencerii mounted in balsam, I cannot detect a trace of lines upon 

 this, and can only satisfy myself of their existence on the speci- 

 mens mounted dry. 



A fuller account of the new test will doubtless soon be fur- 

 nished by Spencer himself. In the meantime the above hasty 

 notice of it is given, to complete my proof that I have not over- 

 rated the powers of our native artist. 



SCIENTIFIC INTELLIGENCE 



I. Chemistry and Physics. 



1. On some New Relations of the Diamagnelic Force; by Prof. 

 Plucker, (Pi-oc. Brit. Assoc, for 1848., Athen., No. 1086.)— Mr. Plucker 

 gave a short account of experiments belonging to a new magnetic ac- 

 tion. A crystal with one optical axis being brought between the two 

 poles of a magnet, there will be a repulsive force, going out from each 

 of the poles, and acting upon the optical axis. According to this action, 

 the crystal, if suspended, will take such a position that its optical axis 

 is placed within the equatorial plane. When the crystal has two optical 

 axes, there will be the same action on both ; according to which, the 

 line b ecting the acute angle formed by the axis will turn into the 

 equatorial plane. When the crystal is suspended in such a way that 

 it may move freely round any line whatever of the plane, containing 

 both axes, this plane will take the equatorial position. Thus a crystal 

 being neither transparent nor showing any trace of its crystalline struc- 

 ture, we may by means of a magnet find the optical axes. At the 

 same time we get a new proof of the connexion between light and 

 magnetism. When light is passing through a crystal, there are in 

 general two directions, where it is effected in quite a distinct way, 

 these same directions are acted upon by a magnet. 



Prof. Faraday contrived to convert two raw potatoes inter representa- 

 tives of the poles of an electromagnet, and by a slice of another, 

 with a quill stuck through it, represented the magnetic or diamagnefic 

 crystal with its optic axes — and thus contrived to convey a distinct idea 

 of the results of Prof. Plucker's discoveries of the relations of the op- 



