GLASS AND GLAZING. 



541 



of the curve, the condensed steam will tied laps are objected to by those who 

 to a great extent pass off outwards. Put- advocate that too much light cannot be 



Fig. 764. 



admitted into a house under any circum- 

 stance, and that the laps rendered opaque 

 by the putty tend to the exclusion of 

 light. This we admit ; but were the laps 

 left unputtied, we maintain that in a 

 very short time the same effect would 

 take place, as the dust and filth, finding 

 their way between them, would exclude 

 quite as much light as the puttied laps 

 do. Others object on the ground that 

 the house would be too close ; but venti- 

 lation, properly conducted, will remedy 

 this. And some are afraid of the con- 

 densation which takes place within ; but 

 ventilation is again the cure ; and open- 

 ings in the middle of each lap about a 

 quarter of an inch in length will allow 

 the condensed steam to escape to the 

 outer surface of the roof. The great ad- 

 vantage of laps is to strengthen the glass, 

 to exclude wet, and to prevent breakage 

 by the expansion of frozen water. 



However effective any or all of the 

 methods hitherto proposed for getting rid 

 of paint and putty as a means for fasten- 

 ing the glass to the wood or metallic 

 parts of hothouses have been, certainly 

 there is room for improvement and hope 

 for success. The methods proposed by 

 Curtis and Harrison, Saul, Kent, Barratt, 

 &c, are all in the right direction ; and 

 we have no doubt that rebated astragals 

 will be soon entirely dispensed with, and 

 others, with their upper sides quite level, 

 substituted. We have constructed some 

 of this form, and bedded the glass on 

 strips of vulcanised india-rubber above 

 one-eighth of an inch thick. On this 

 the glass is laid ; and over the joinings of 

 the panes another similar strip of the 

 same material, half an inch in breadth. 

 Over this is laid a bead of glass, rounded 

 slightly at top, and perforated with holes 

 12 inches asunder and one-eighth of an 



inch in diameter, passing through the glass 

 bead and astragal. Into this perforation 

 Jeffrey's marine glue, or vulcanised india- 

 rubber, is poured in a liquid state, and re- 

 ceived at the lower side of the astragal into 

 a small capsule, which, when removed after 

 the material has cooled down and harden- 

 ed, leaves it similar to the head of an ordi- 

 nary screw. The top part is moulded in the 

 same manner — the little funnel through 

 which the liquidised india-rubber is poured 

 being about a quarter of an inch in dia- 

 meter, and of circular form. When the 

 liquid is poured in and beginning to 

 solidify, this funnel is removed, and the 

 portion which is above the glass beading 

 is moulded by the finger and thumb, 

 while yet soft, in form of a button. Glass 

 so secured is much more firmly attached 

 to the framework than by any other 

 method, and will remain for years in the 

 same state. When repairs become neces- 

 sary, or new glass is put in, the head of 

 either end of this tie of india-rubber is 

 cut or filed off ; and with a pair of 

 nippers applied to the other end, the 

 whole is withdrawn, both out of the astra- 

 gal and glass bead, with perfect ease. 

 The glass beading is lifted off, the square 

 of new glass laid in its place, and again 

 secured as already explained. The elas- 

 ticity of the vulcanised india-rubber is 

 such that no ordinary concussion, vibra- 

 tion, or pendulous motion can break or 

 disturb the glass resting upon it, and kept 

 down by it, under the glass beading. 

 The coping formed by the glass bead 

 covers the india-rubber so completely as 

 to keep it dry, and also to prevent the 

 entrance of wet to the astragal ; and the 

 whole surface of the roof is one continuous 

 sheet of imperishable glass, without paint 

 or putty, wood or metal. 



Mr Spencer's mode of glazing has been 



