400 Descriptions of Three Neiv Pears. 



The relative temperatures indicated by good therpiometers, 

 placed behind the glasses and fluid cells, will show these 

 effect's in a clearer light. The foregoing results present a 

 fair average series, and distinctly mark the relative degrees 

 in which the media are permeable by the heating rays. 



No investigations or experiments on glass have come un- 

 der our observation so reliable, and so valuable in practical 

 horticulture, as those we have given in the foregoing pages, 

 and which will be more practically shown in subsequent 

 papers. What the gardener wants is not mere speculations 

 upon the possible influence of this or that kind of glass, or 

 other media to which his plants are subjected. He wants a 

 plain and intelligible explanation of those influences which 

 he sees daily in operation during occupation. He wishes to 

 know what are the causes of the burning of his vine leaves, 

 under some kinds and colors of glass, and not under others, 

 and why the sun's rays have so much more influence on 

 plants when permeating atmospheres of various density or 

 humidity. This we will endeavor to elucidate in our subse- 

 quent remarks, and in a manner as clear as can be evolved 

 from ascertained facts, that the most unscientific may clearly 

 comprehend them. 



Roxbury, August 17, 1852. 



(To be continued.) 



Art. IV. Descriptiojis and Engravings of Three New 

 Pears. By Baptiste Desportes, Angers, France. 



[In our present volume we have already given the descrip- 

 tions and engravings of three new pears, by our correspondent 

 M. Desportes, of Angers, France. We now have the pleasure 

 of presenting the descriptions of three more varieties, two 

 of which are quite new, and one of them of remarkable size 

 and superior quality. We are highly gratified in being able, 

 through the kindness of M. Desportes, to bring these many 



