ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 627 



is necessary, in order to obtain a greater magnification, to still further 

 diminish this small distance, this instrument gives at 25 cm. an amplifi- 

 cation more than 12 diameters. Hence it offers facilities for observing 

 insects without frightening them or forcing them to quit their natural 

 habits. Thanks to its large field, and to its property of seeing several 

 planes at once, the instrument is equally suitable for observing a large 

 plant. An extraordinary effect of relief is also produced, comparable to 

 that of a stereoscope. 



In reality the telemicroscope is only a telescope of a special kind. 

 Its objective is composed of two achromatic lenses separated by a dis- 

 tance less than the principal focal distance of the most convergent ; 

 therefore they act as one. Achromatism is increased by this arrange- 

 ment, whence results the clearness of the images. The objective is 

 Dollond's with four plano-convex glasses. The eye-piece has been 

 chosen as convergent as possible, in order to increase the enlargement 

 and the extent of the field without affecting the clearness. 



Amici's Microscope. — The following interesting holograph letter 

 from Prof. Amici, together with a description of his Microscope, has been 

 recently found among the papers belonging to the Society. 



Mr. John B. Carruthers, F.L.S., has most kindly translated the letter, 

 together with the description of the Microscope. The cuts are photo- 

 graphic reproductions of Prof. Amici's own drawings. It will be recol- 

 lected that Amici was the first to demonstrate the part played by the 

 pollen-tube in the fertilisation of flowering plants. 



" Most Honoured Sir, 



" I send you the description of the Microscope which you have ob- 

 tained, and the flat glasses necessary for the observations. I add also 

 the ground glass which is mentioned in describing the use of the in- 

 strument. When the objects are prepared, I shall make it my duty to 

 send you some which will serve as specimens, and will show the com- 

 parative power of the Microscope. With high esteem, I am your obe- 

 dient servant, 



" G. Batta Amici. At home. 18 Dec. 18-11." 



" Amici's upright Microscope, acquired by Mr. Sebright, contains ten 

 achromatic objectives, variously marked, which are used combined in 

 series of two, three, or even four, united together. Figs. 2", 3", 4", and 

 5 a [fig. 155] show the series as they ought to be fixed below the tube of 

 the Microscope to obtain different magnifying powers. 



" The four objectives marked with dots form the strongest combina- 

 tion ; their focal distance being very short, only permits their use with 

 minute transparent bodies, which bodies, if immersed in a fluid, should 

 be observed by covering them with a very thin plate of mica, so as not 

 to wet the last, that is to say the lowest, lens, which is brought almost 

 into contact with them. 



" The combination of objectives marked 3, 2, 1, in the order shown 

 in fig. 3", serves only for transparent objects, but has been constructed 

 so that, in order to see these objects clearly and distinctly, they must 

 be enclosed between two flat glasses of which the upper one (i.e. the one 

 which covers the object) must be 1 mm. in thickness. For this pur- 

 pose the instrument is provided with a good number of cover-glasses of 



