354 SCIENCE IN SHORT CHAPTERS. 



tion of such a conservatory is so simple that any industrious 

 artisan or clerk with any mechanical ingenuity could, with 

 the aid of a boy, do it all himself. No special skill is re- 

 quired for any part of the work, and no other tools than a 

 rule, a saw, and a hammer. Side posts and stronger end 

 rails would in some cases be demanded. 



I have not been able to fairly carry out this project, inas- 

 much as I reside at Twickenham, beyond the reach of the 

 black showers of London soot. I have, however, made 

 some investigations relative to the climate which results 

 from such enclosure. 



This was done by covering a small skeleton frame with 

 the canvas, putting it upon the ground over some cabbage 

 plants, etc., and placing registering thermometers on the 

 ground inside, and in similar position outside the frame ; 

 also by removing the glass cover of a cucumber frame, and 

 replacing it by a frame on which the canvas is stretched. 



I planted 300 cabbages in November last, in rows on the 

 open ground, and placed the canvas-covered frame over 18 

 of them. At the present date, March 15, only 26 of the 

 282 outside plants are visible above the ground. All the 

 rest have been cut off by the severe frost. Under the frame 

 all are flourishing. 



I find that the difference between the maximum and the 

 minimum temperatures varies with the condition of the 

 sky. In cloudy weather, the difference between the inside 

 and the outside rarely exceeds 2 Fahr., and occasionally 

 there is no difference. In clear weather the difference- is 

 considerable. During the day the outside thermometer re- 

 gisters from four or five to seven or eight degrees above that 

 within the screen during the sunshine. At night the mini- 

 mum thermometers show a difference which in one case 

 reached 14, i.e., between 23d and 24th February, when 

 the lowest temperature I have observed was reached. The 

 .outside thermometer then fell to 8 Fahr.. the inside to 

 22. On the night of the 24th and 25th they registered 

 15 outside, 25^ inside. On other, or ordinary clear frosty 

 nights, with E. and N. and N.E. winds, the difference has 

 ranged between 4 and 6, usually within a fraction of the 

 average, 5. 



