Meteorological Observations. 79 



silica in these Phvtolitharia, as well as in the Diatomacese, Polycvsti- 

 ncse and Spongiolites, is not doubly refractive. He makes an excep- 

 tion in the case of the shell o{ Arachnoidiscvs, but my own experiments 

 prove that when properly cleaned this shell forms no exception. As 

 1 have shown above that the silica in the cuticle of the Equisetnm 

 and Grasses agrees with that in the lower tribes in characters, I think 

 the conclusion is warranted, that doubly refractive silica has no ex- 

 istence in the organic world. — Sillimans American Journal for May 

 185G, p. 357. 



METEOROLOGICAL OBSERVATIOXS FOR MAY ].856. 



Chmnick. — May 1. Overcast : cold showers, partly hail : clear and cold. 2. 

 Quite clear : cloudy : frosty at night. 3. Cloudy and cold : showery. 4. Overcast : 

 cloudy : clear, with sharp frost at night. 5. Frosty early a.m. : cloudy and cold. 



6. Fine : cloudy and cold : rain. 7. Cold rain. 8. Densely clouded : cold north 

 wind. 9. Heavy clouds. 10. Uniforndy overcast : fine. 11. Light haze : fine : 

 cloudy. 12. Uniform haze : rain. 13. Rain : cloudy. 14. Heavy sliowers. 15. 

 Fine: showers, with some hail. IG. Fine. 17. Cloudy. 18. Boisterous, with 

 rain and hail. 19. Verv fine. 20. Very fine: slight frost. 21. Fine: rain. 

 22. Rain. 23. Cloudy : fine. 24. Fine. 25. Cloudy : rain. 26. Fine. 27. Very 

 fine : heavy rain at night. 28. Cloudy : very fine. 29. Hazy : cloudy : fine. 30. 

 Cloudy and cold. 31. Rain. 



Mean temperature of the month 50'-09 



Mean temperature of May 1853 48 "78 



Mean temperature of May for the last thirty years 53 "35 



Average amount of rain in May 1*852 inches. 



Boston. — May 1. Cloudy : rain and sleet p.m. 2, 3. Cloudy : rain and hail p.m. 

 4,5. Cloudy. 6. Cloudy : hail and snow a.m. 7. Cloudy. 8. Cloudy : rain a.m. 



9, 10. Cloudy. 11. Fine. 12, 13. Cloudy. 14. Cloudy : rain with thunder p.m. 

 15, 10. Cloudy. 17. Cloudy: rain p.m. 18. Cloudy: rain a.m. and p.m. 19. 

 Cloudy. 20, 21. Fine. 22. Rain .a.m. and p.m. 23. Fine : rain and thunder p.m. 

 24. Cloudy : rain a.m. and p.m. 2;), 20. Cloudy : rain p.m. 27 Fine : rain p.m. 

 28. Cloudy : rain a.m. and p.m. 29. Cloudy : 30. Fine. 31. Cloudy : rain p.m. 



Sandxcick Manse, Orkney. — May 1. Bright a.m. : cloudy p.m. 2. Sleet-showers 

 A.M.: cloudy p.m. 3 — 5. Cloudy ^.u. and p.m. 6. Cloudy a.m.: clear p.m. 



7. Clear a.m. and p.m. 8. Cloudy a.m. : clear p.m. 9. Clear a.m. : rain p.m. 



10. Cloudy A.M. : drops p.m. 11. Drizzle a.m. : fog p.m. 12. Hazy a.m. : clear, 

 fine P.M. 13. Cloudy a.m. and p.m. 14. Cloudy a.m. : rain p.m. 15. Cloudy a.m. 

 drops p.m. lb. Bright a.m. : cloudy P.M. 17. Clear, fine a.m. : cloudy, fine p.m. 

 18. Showers, hriglit a.m. : showers p.m. 19. Cloudy a.m.: showers p.m. 20. 

 Bright A.M. : clear p.m. 21, 22. Bright a.m. : cloudy p.m. 23, 24. t loudy a.m. 

 and p.m. 25. Clear a.m. and p.m. 26, 27. Cloudy a.m. and p.m. 28. Bright a. m : 

 cloudy P.M. 29 — 31. Clear a.m. and p.m. 



Mean temperature of May for previous twenty-nine years ... 47'"85 



Mean temperature of this month 46 "83 



Mean temperature of May 1855 43 81 



Average quantity of rain in May for fifteen previous years ... 1-66 inches. 



The great drought continues ; the rain during the last three months heing 

 less than the average for May alone, ^^hich is our driest month, and not half the 

 quantity that fell in March aloue last year. 



