Meteorological Observations, 79 



silica in these Phytolitharia, as well as in the Diatomaceee, Polycysti- 

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

 tion in the case of the shell o^ Arachnoidiscus, but my own experiments 

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

 I have shown above that the silica in the cuticle of the Equisetum 

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

 the conclusion is warranted, that doubl)'- refractive silica has no ex- 

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

 1856, p. 357. 



METEOROLOGICAL OBSERVATIONS FOR MAY 1856. 



Chiswick. — 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. Uniformly overcast : fine. 11. Light haze : fine : 

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

 Fine: showers, with some hail. 16. 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 1855 48 '78 



Mean temperature of May for the last thirty years 53 '55 



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, 16. 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. 25, 26. 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. 



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

 A.M. : cloudy p.m. 3 — 5. Cloudy a.m. 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. 16. Bright A.M. : cloudy P.M. 17. Cl^ar, fine a.m. : cloudy, fine p.m. 

 18. Showers, bright 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. Cloudy 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 being 

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

 quantity that fell in March alone last year. 



