INTRODUCTION. XXV 



crevices, which every glass-house must possess. 

 Before assigning the excess of sulphurous and muri- 

 atic acid gases as the deleterious property of atmo- 

 sphere, obviated by Mr. Ward's plan, Mr. Ellis should 

 have shown us that this excess was so obviated. He 

 should have shown us that the deleterious gases did 

 not exist within ; he should have tested the interior, 

 and given us the result ; he should have told us by 

 what mystic character engraved on the threshold these 

 gases were scared away; in short, he should have 

 done what he has not done he should have analyzed 

 facts rather than assumed them. The small inquiring 

 class, finding triat this important link in the chain of 

 argument is deficient, will be apt to think that the 

 lapse of that single link sets adrift the entire cargo 

 of conclusions. 



Having dismissed the gases with the alternative, 

 that either they do not exist in any undue proportion 

 in Mr. Ward's fernery and its neighbourhood, or that 

 they do exist, and are not injurious to vegetation ; hav- 

 ing seen also that fuliginous matter does exist in the 

 atmosphere to a great extent, that it is highly injuri- 

 ous to the growth of vegetables, and that it is excluded 

 by Mr. Ward's plan, we shall perhaps be expected, 

 without further inquiry, to conclude that in the 

 exclusion of fuliginous matter rests the whole secret 

 of its effect. To this I must demur, or the use of 

 these closed cases would be confined to London and 

 similar smoky atmospheres ; whereas it is well known 

 the sphere of their utility is universal. Every culti- 



d 



