nS [ASSOIBLV 



gtanccsj gave a deflection of f^lo of an inch, and a permanent set 

 of yilff of ^^ inch. The bearings in your machine are only about 

 twenty-eight inches apart, so that the power required to mi.ke the 

 deflection is very much increasedjand yet the machine does not seem 

 to feel the work. 



We have no hesitation in recommending the machine in the highest 

 terras, for straightening rails, and for all purposes where great pressure 

 is required. Ita simplicity and comparative cheapness must certainly 

 bring it into very extensive use, and for an immense variety of appli- 

 cations. 



With our best wishes for your success, we are, 



Very respectfully, 



Your ob't servants, 



COOPER & HEWITT. 



EQUATORIAL TELESCOPE, 

 Made by Henry Fitz, New-York. 



Telescopes date no farther back than about the commencement of 

 the 17th century. With the aid of a telescope of rude and imperfect 

 construction, Galileo observed the satellites of Jupiter about the year 

 1610. Telescopes are of two kinds, refracting and reflecting. Re- 

 fracting telescopes were constructed first, but the compound nature 

 of light presented difficulties, which for a time were regarded as insur- 

 mountable. Reflecting telescopes therefore were for a long time 

 used, during which they attained a degree of perfection. The diffi- 

 culties attending the construction of the reflecting telescope, were at 

 length overcome through the persevering efforts of John Dolland of 

 London, who produced an achromatic refracting telescope about the 

 year 1757. The discoveries of Frauenhofer have contributed to the 

 improvement of telescopes. At the present time they are cxtren- 

 sively made in London by the descendants of Mr. Dolland rnd others. 

 We are credibly informed that they rely for their glasses principally 

 on the manufacturers on the continent, Merz, the successor of Frauen- 

 hofer, and one or two besides. 



