198 Miscellanies. 



Specific gravity, a mean of several trials, 2,88. Effervesces slight- 

 ly with acids. Color, greyish white ; with a faint tinge of blue. In 

 plates, varying from one sixteenth to one inch in thickness. Struc- 

 ture, coarse fibrous ; fibres parallel. Lustre silky, and exhibits a 

 changeable play of color. Not so chatoyant as satin spar. 



It forms seams, both horizontal and vertical, in secondary sand- 

 stone. The banks of the river vary in height from thirty to sixty 

 feet. The water descending from the high ground towards the river 

 has formed numerous ravines. One of these ravines has a pave- 

 ment of arragonite. Its hardness, superior to that of the marie, has 

 prevented the destruction of the lower strata. 



It is associated with calcareous spar in nests, in sandstone and 

 variegated marie. 



11. Thomson's Scientific Medals ; by J. Finch. — There have 

 been recently published in England a beautiful series of scientific and 

 philosophical medals. They are sixteen in number, three inches in 

 diameter, and are struck either in tin or silver. The figures and 

 impressions are executed in a very superior manner ; they contain 

 condensed tabular views of the sciences, very useful to the student, 

 and figures of the steam engine, hydraulic press, mountains, he. 



Medal. Obverse. Reverse. 



No. 1. Mechanics, - - - Mechanics. 



2. Optics, - - - - Optics. 



3. Electricity, . - - Galvanism. 



4. Hydrostatics, - - - Hydraulics and Pneumatics. 



5. Metallurgy, _ - - Specific Gravities. 



6. Chemistry, _ - - Chemistry. 



7. Astronomy, _ - - Astronomy. 



8. Mineralogy, _ - - Mineralogy. 



9. Geology, _ - - Geology. 



10. Crystallography, - - Crystallography. 



11. Mountains, _ - - Classification of minerals. 



12. Phrenology, - - - Phrenology. 



13. Marquis of Worcester and ^ rp .i • , ^r. u- i 



^^ . _ if 1 revethick on the high pres- 



Captam Savery on the > 



L sure. 

 Steam Engine, ) 



14. Newcomen and Beighton > Perkins on the high pres- 



on ditto. S sure. 



15. Watt's Single for raising water, Watt's single. 



16. Watt's Double for driving ") Watt's double with every im- 



Machinery, > provement. 



