ON THE ITALIAN EXHIBITS. 199 



"rocchetto," swings, passing successively from the contact of the 

 first magnet, to that of the second, and then back to the first again, 

 and so on. 



Then, by making use of the great natural magnet of the Regio 

 Istituto Superiore di Firenze, a very large parallelepiped of about 

 50 x 65 X 78 centimetres in dimension, and fastening the keeper with 

 isolated thread, they were easily able by detaching it, interrupting at 

 the same time the inducted current, to obtain the spark and every 

 other effect peculiar to electricity. 



And with regard to Nobili, allow me to remind you that, besides his 

 important researches in electro-physiology ; on rotary magnetism (di 

 rotazione) ; on electric-dynamical phenomena, &c., he founded his 

 electrical condensator upon the principle of the extra current, upon 

 -which, shortly afterwards, so much light was thrown by your illustrious 

 Faraday. It consisted of a " rocchetto" of thread interposed in the 

 circuit of the electrical current, which acted in such a manner that the 

 spark of opening (d'aperturd) was greatly increased in intensity. 



And now turning to Amici, I am sure that all will recognise in him 

 a remarkable scientific man, of very remarkable mechanical genius, 

 and one who has bestowed his name on many valuable and useful in- 

 struments. He was especially noted for his microscopes and tele- 

 scopes, two of which are among the most honoured objects in the 

 observatory of Arcetri. One of the objectives has a diameter of 

 twenty-nine centimetres. The two microscopes which you now see 

 before you, although not among the best of those made by Amici, 

 are, however, the oldest In one of them you may observe how the 

 objective is made by means of a concave glass ; among the acces- 

 sories you will find various systems of camera lucida, some of them 

 were imagined by him ; and you can likewise see ingenious methods 

 for concentrating light, especially on opaque bodies. 



I cannot conclude this hasty review without reminding you of 

 Matteucci, of whom science was, alas ! too quickly robbed. The 

 greater number of us have constantly present in our minds the weighty 

 judgment pronounced upon his works by the most illustrious scientific 

 men of Europe ; and many venerable institutions inscribed his name 

 ?n their lists of members. The fact that your Royal Society for the 

 Advancement of Science granted him the Copley Medal frees me 



