518 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



vation with the vertical tube cutails upou the muscles of the 

 neck. 



The prism, imless badly made, does not interfere with the defini- 

 tion of the objective, even when used upon Ampliipleura 'pcllucida. 



The same prisms were adopted by M. Nachet in his double-bodied 

 Microscope for two observers. 



Old Italian Microscope, — In a pamphlet in Italian entitled 

 ' Nvove invcntioni di tubi ottici dimostrate nell' Accaderaia Fisico- 

 matematica Komana I'anno 1686' (19 pp. and 3 pis.), wliich con- 

 cludes with the signature of " Carlo di Napoli Dottoi- nell' vna, e 

 I'altra Legge Prosecretario," several quaint forms of Microscopes and 

 telescopes are described. One of the most carious of the Microscopes 

 is that shown in fig. 100 (reduced from the original fig. to about 

 2/3 size.) 



Fig. 106. 



The speciality of the instrument consists in two points. (1) The 

 objects arc placed round the circumfurcnce of a wheel which has two 

 motions ; one on its axis for bringing the dificrent objects under the 

 lens, and a second motion of the whole wheel laterally by rotation 

 of its screwed axis, by which means all parts of the objects can bo 

 observed by the lens. (2) The adjustment for focus is effected by 

 the Very primitive device of fixing the lens at the end of a spring, to 

 which a curd is also attached. On winding up the cord on a screw 

 T>eg, the si)riug is bent and the lens brought closer to the object. On 

 reversing the motion the spring is relaxed again and the lens with- 

 diawn. 



