Portraits iniyaguerreoiype : —Meteorological Observations. 535 



That chromate of lead is very easily converted by means of carbon 

 and hydrogen into a mixture of oxide of chrome and metallic lead. 



This mixture by heating is in a state to combine with oxygen j 

 and this combination takes place not only with the metallic lead, 

 but also with the oxide of chrome. 



By heat alone it is very difficult to deprive chromate of lead of 

 oxygen. It is at first converted into a mixture of basic chromate 

 of lead and oxide of chrome : in order to reduce all the chromic 

 acid into oxide of chrome, an uncommonly highly temperature is re- 

 quired. 



When a mixture of oxide of chrome and oxide of lead is heated, 

 it is also converted into basic chromate of lead and oxide of lead. 



It is therefore chromate of lead, which is often employed in or- 

 ganic analysis, from which this latter mixture is derived. — Journal 

 fiir Praktische Chemie, No. 2. 1840. 



PORTRAITS IN DAGUERREOTYPE. 

 Professor Draper, of the University of New York, informs us in 

 a note dated March 31st, that he has succeeded during the winter 

 in procuring portraits by the Daguerreotype, and that they have all 

 the beauty and softness of the most finished mezzotint engraving, and 

 only require from 20 to 45 seconds for execution. 



METEOROLOGICAL OBSERVATIONS FOR APRIL, 11 



Chiswick. — April L Slight rain : cloudy. 2. Hazy: very fine. 3. Cold dry 

 haze : frosty at night. 4 — 6. Very fine. 7. Fine : stormy showers at night. 

 8. Slight showers. 9. Cloudy and cold. 10 — 12. Very fine. 13 — 17. Fine bus 

 very dry. 18. Clear, hot and dry. 19. Hazy : very fine. 20. Very fine. 21 — 

 23. Cloudy and fine. 24. Very fine. 25. Very hot, nearly cloudless, and ex- 

 cessively dry. 26, 27. Hot and dry. 28. Excessively hot for the period of the 

 season, thermometer 81° in the shade. 29,30. Very fine: hot and dry. This 

 month is remarkable for the limited quantity of rain and for a high temperature; 

 the latter being the consequence chiefly of a powerful direct solar lieat, which 

 overcame likewise the counteracting effects of north and north-east winds, for 

 tliey were in fact more prevalent than those from the opposite direction. 



Boston. — April 1. Cloudy: rain p.m. 2. Rain. 3 — 5. Fine. 6. Cloudy. 



7. Cloudy : stormy with rain p.m. 8. Cloudy: hail and rain p.m. 9 — 11. Fine. 

 12. Rain: rain early a.m. 13—19. Fine. 20—24. Cloudy. 25—29. Fine, 

 30. Cloudy. 



Applegarih Manse, Duiiifries-shire. — April 1. Mild day with a shower. 2. Keeri 

 and cold but dry. 3, 4. Dry and more temperate. 5. Fine day after a very 

 slight shower. 6. Stormy day with showers, though slight. 7. Keen cold day. 



8. More moderate. 9. Fine mild day. 10. The 5iarae : slightly moist and 

 cloudy. 11. Drizzling all day, but very lightly. 12. Fine though cold : slight 

 rain P.M. 13. Fine soft slight rain. 14. Charming spring day. 15. Thesame: 

 with frost rime A.M. 16,17. Fine but coldish : frost rime again. 18. Very fine 

 warm day. 19. Thesame: white rime a.m. 20. The same: slight showers 

 P.M. 21. The same: gentle shower. 22. Thesame: moisture. 23. Dry but 

 threatening. 24. The same : cleared up. 25 — 28. Beautiful day. 29. The 

 same, but cloudy. SO. The same : very warm. 



Sun shone out 29 days. Rain, very slight, fell 6 days. Frost, rime 4 days. 



Wind north 1 day. North-east -J day. East-north-east 2 days. East 3 days. 

 East-south-east 1 day. South-east | day. South-south-east 2 days. South 7 

 days. South-south-west 1 day. South-west 7§ days. West-south-west 1 day. 

 West 2^ days. « North-west 1 day. 



Calm 15 days. Moderate 8 days. Brisk 3 days. Strong breeze 3 days. 

 Boisterous \ day. 



