r 



Meteorological Observations. 479 



properli/ employed*, has great advantages over the use of the expensive 

 alkaline stannates. 



4. Dark colours containing tin may be conveniently made by this 

 means. — Journ.fiir Prakt. Chem. Ivi. p. 366. 



REMARK ON ART. LVIII. (oF PHIL. MAG. FOR NOVEMBER) BY 

 MR. SYLVESTER, "THAT THE NON-EXISTENCE OF REAL ROOTS 

 IN ANALYTIC GEOMETRY CORRESPONDS TO THE REDUCTIO AD 

 ABSVRDUM OF EUCLID." 



All imaginary results are e.xpressible by a + i v^ — 1 +/— cv/ — 1 ; 

 and if c=b, we have a real result. Hence if we try the case of one 

 of two presumed equal quantities exceeding the other, this is equi- 

 valent to taking b^-c; if less, to 6 < c ; in both cases an imaginary 

 result would follow. But if the algebraic treatment resulted in 6=c, 

 we should necessarily find V — 1 disappear, and the presumed equa- 

 lity would really exist as «+/. This being the geometric process 

 generally followed in the reductio ad absurdum, may perhaps throw 

 some light on the verification of Mr. Sylvester's important suggestion. 

 23 Walpole Street, Chelsea, S. M. Drach. 



November 22, 1852. 



METEOROLOGICAL OBSERVATIONS FOR OCT. 1852. 

 Chiswick. — October 1. Fine. 2. Uniformly overcast : very fine : clear. 3. Clear : 

 very fine : clear : slight rain. 4. Constant and very hea\7 rain : clear. 5. Clear 

 and boisterous. 6. Rain : clear at night. 7. Cloudy : fine : uniformly overcast. 

 8. Overcast: fine. 9. Clear : very fine : rain. 10. Overcast. 11,12. Veiy fine. 

 13. Fine : dusky haze. 14. Foggy : xiniform haze : at night clear above, hazy 

 near the horizon. 15, 16. Foggy : cold haze : clear above at night. 17. Dense 

 fog. 18. Very fine throughout. 19. Foggj' : very fine: dense fog at night. 

 20. Foggy: exceedingly fine : hazy. 21. Foggy: hazy: rain. 22. Hazy: rain. 

 23. Cloudy : rain. 24. Cloudy : very fine : heavy rain at night. 25. Heavy rain : 

 clear at night. 20. SMght fog : rain. 27. Rain. 28. Densely overcast : cloudy : 

 clear. 29. Clear : overcast : rain. 30. Overcast : rain. 31. Clear and fine : bright 

 sun : overcast at night. 



Mean temperature of the month 46°-38 



Mean temperature of Oct. 1851 51*25 



Mean temperature of Oct. for the last twenty-sLx years ... 50 -50 



Average amount of rain in Oct 2-60 inches. 



Boston. — Oct. 1, 2. Fine. 3. Cloudy : rain early a.m. 4, 5. Cloudy : rain a.m'. 

 and P.M. G. Cloudy : rain p.m. 7. Fine : rain early a.m. 8, 9. Fine. 10. Cloudy! 

 11—13. Fine. 14. Foggy. 15—17. Cloudy. 18. Fine. 19. Cloudy. 20. Fine.' 

 21,22. Rain: rain a.m. 23. Cloudy: rain a.m. 24,25. Fine. 20. Fine: 

 rain p.m. 27. Fine : rain a.m. and p.m. 28. Rain : rain a.m. 29, 30. Cloudy! 

 31. Fine : rain early a.m. 



Sandwick Manse, Orkney. — Oct. 1. Clear : lioar-frost : fine : lioar-frost. 2. Rain. 

 3. Bright : showers. 4. Cloudy. 5. Cloudy : clear. C, 7. Sleet-showers. 8. 

 Slect-sliowcrs : cloudy. 9. Drizzle: cloudy. 10. Showers. 11,12. Bright: 

 cloudy. 13. Kain : cloudy. 14. Cloudy: fine. 15. Bright: clear: fine. 16. 

 Fine : hoar-frost : liazy : fine. 17. Fine: cloudy: rain. 18. Raiu : cloudy. 19. 

 Drizzle. 20. Cloudy: drizzle. 21. Fine: cloudy: fine. 22. Hazy: drizzle. 

 23. Cloudy: clear: fine. 24. Clear: fine: aurora. 25. Clear: fine. 20,27. 

 Showers. 28. Showers : bright : clear. 29. Cloudy. 30. Showers. 31. Rain: 

 cloudy. 



Mean temperature of Oct. for twenty-five previous years 47°-55 



Mean temperature of this month 46 -88 



Average <iuantity of rain in Oct. for si.v years 4-39 inches. 



* Tlic mode of employment is not stated by the author. 



