HARDWICKE'S SCIENCE-GOSSIP. 



129 



first, on carelessly looking at it, it appeared to be 

 explained by that disintegration which gives rise to 

 those beautiful iridescent scales on old glass, and 

 especially in the old black glass Dutch bottles, whose 

 surface, on removing the scales, presented somewhat 

 the appearance described. My friend informed me it 

 was considered by some to have been made by the 



95 is a portion seen by reflected light of the surface of 

 some dark green glass twice its natural size, which 

 shows the general arrangement. On submitting 

 them to microscopical examination, to my delight, 

 all the edges of these masses appeared to be spiked, 

 and, although they had been in my friend's possession 

 for thirty years, showed the cellular structure deline- 

 ated in fig. A (Hartnack, ob. 7, oc. 2, tube drawn 

 out), being the portion C of fig. B (Hartnack, ob. 4, 

 oc. 4, tube in). I have shown them to two botanists, 

 who are quite satisfied as to their nature ; but they 

 asked the question as to whether they might not be 

 lichens which had occupied already existing holes; 

 this, however, was capable of denial on the following 

 grounds. It will be observed in fig. D that the bodies 

 commenced to grow at certain points, but as they 

 became larger they also became confluent, forming 

 irregular masses with a serpiginous margin, to which the 

 depression in the glass always corresponds ; the central 

 portion of each depression is level, and however large 

 it may be, it is of the same depth, the steep edges 



Fig. 93. Cellular Structure, of Glass-eating Lichen (mag.). 

 See fig. 94, at c. 



Fig. 95. Lichen as 

 seen by reflected 

 light on green glass. 



Fig. 96. Erosions running in nearly 

 straight lines. 



Fig. 94. Glass-eating Lichen (mag.). 



workmen, to give a better effect to the light ; but the 

 irregularity sets that question at rest directly, though 

 it stimulated me to look into the matter more care- 

 fully, and on a careful examination I was fully satis- 

 fied that each depression was occupied by a small 

 lichen, such as we see covering grave-stones ; at figure 



being occupied by the growing processes which seem 

 alone to have the absorbing power ; and lastly, on 

 removing the growth by various re-agents, the exact 

 figure of the points and even in some instances of 

 the individual cells, are seen beautifully cut and em- 

 bossed upon the glass. It occurs on the side opposite, 

 and not on the painted side, which, in glazing, is 

 placed on the inside of the window, and therefore 

 would be unfavourable to the growth of these plants ; 

 neither does it occur round the edges, which are over- 

 lapped by the lead. One point was at first puzzling ; 

 these erosions sometimes appearing to run in straight 

 lines, as seen in fig. E ; it could, however, be de- 

 monstrated by a magnifying glass that it occurred 

 along old scratches, the rough surface of which had 

 afforded the most easy attachment for the spores and 

 young plant. It is to my friend, Mr. T. Coates 

 Archer, to whom I am indebted for the specimens, 

 and also for a few notes as to their history. They 

 are from the Church of Little Dunmow, in Essex 

 (celebrated for the annual distribution of a flitch of 

 bacon), from which it was removed by some glazier 

 of Felsted, from whom my friend bought it, and has 

 now had it over thirty years. 



