Xliv PROCEEDINGS. 



" It is now six months since the fitness of Kolled 

 Rough Plate Glass to supersede the common sheet was 

 suggested. The impossibility of obtaining the latter, with 

 any certainty that it will not burn the leaves beneath it, had 

 become notorious, and cheap rough plate was suggested as 

 a substitute. This kind of glass is made of the same mate- 

 rials as sheet, but by a very different process. Instead of 

 being in the first instance blown into the form of a cylinder, 

 or ' mufi^',' then slit and flattened — a difficidt process, inca- 

 pable of making it level or free from large irregular lenses — 

 rough plate is at once rolled into plates, and left with an 

 irregular granulated surface, which breaks and bends and 

 separates the rays of light as they pass through it, thus 

 rendering their concentration, and the burning consequent 

 upon it, impossible. But it was objected, by those whose 

 opinion in all practical matters has deservedly the greatest 

 weiofht, that, althono-h this rouQjh glass might be suitable 

 for glazed structures in the summer, it could not be safely 

 employed in winter ' because of the small quantity of light 

 that was able to pass through it ;' and that, therefore, any 

 advantage that might attend it in one season would be 

 counterbalanced at another. This was entirely at variance 

 with my own opinion ; I saw no difference in the quantity 

 of light that passed through : on the contrary, the amount 

 appeared to be the same in both cases, the difference being 

 that, by rough plate, light was dispersed, and by conunon 

 sheet concentrated, or at least not interfered with by dis- 

 persion. It was, however, felt that the objections taken to 

 the former would be better answered by an experiment than 

 by any man's opinion ; and therefore the Garden Committee 

 directed it to be tried in the Garden. 



" For this purpose a small pit, unventilated except by 

 sliding the sashes, and heated by hot-water pipes, ^^•as 

 selected. In the last week of August this pit was filled 

 with soft-wooded plants, which can only be kept in health 

 in the presence of a large quantity of light, among which 

 were the following, viz. : the Begonias odorata, undulata, 

 argyrostigma, and dichotoma, Torenia asiatica, Pentas 

 carnea, Adamia sylvatica, Calostylis aurantiaca, and Achi- 

 nienes picta. The four Begonias, Calostylis, Adamia, and 

 Pentas had been cut close back, and were leafless, Torenia 

 was a cutting just struck, and of Achimenes the dry tubers 

 were employed. The experiment was thus set in action, 

 without any special care having been taken to make it 

 succeed ; on the contrary, everything was against success. 



