164 



HORTICULTURE 



February 9, 1907 



GREENHOUSE CONSTRUCTION. 



A Paper Read Before the American Carnation Society by R. O. King. 



During the past few years many 

 papers have been read on greenhouse 

 construction. The general methods of 

 construction have been very thorough- 

 ly described and most of the growers 

 are agreed for Instance, that cypress 

 is about the best thing to use for the 

 wood work, that iron posts are better 

 than wood posts, that an Iron gutter 

 Is better than a wood gutter, etc. All 

 of these things are so familiar that It 

 Is hardly worth while going into fur- 

 ther discussion about them. It will 

 perhaps be more interesting to take 

 up some points of greenhouse con- 

 struction which are just as important, 

 but which have not received as much 

 attention. For instance, the use of 

 glass up to 24 inches in width makes 

 a lighter and less expensive house 

 than narrow glass. The choice of lo- 

 cality for a greenhouse plant should 

 depend among other things on the 

 amount of light available. The ap- 

 plication of the scientific principles 

 used in the design of large buildings 

 and bridges to greenhouse construc- 

 tion is something which should Inter- 

 est the grower as well as the designer. 

 The application of these principles 

 has not been necessary in the ordi- 

 nary construction of small houses 

 where the accumlated experience of 

 many years has been a sufficient 

 guide. When, however, it is necessary 

 to design a house unlike anything pre- 

 viously constructed there is of course 

 no experience to fall back on, so a 

 safe design can only be worked out by 

 the application of the scientific meth- 

 ods referred to. 



WIDE GL.\SS. 

 Some years ago 16 inch glass was 

 considered about the limit for green- 

 house construction. More recently 

 18 inch glass has been used. In 

 Canada a number of plants are built 

 with 20 inch double diamond English 

 glass. Twenty inch glass is probably 

 selected because 20 Inches square is 

 a good size for butting and it does 

 not exceed 40 united inches. In the 

 United States where lapped glass is 

 most generally used the size most in 

 use is 16x24 with the bars 16 inches 

 apart. A few of the more daring grow- 

 ers have risked building their houses 

 ■with the bars 24 inches apart and using 

 this same size glass. In our own ex- 

 perience a number of customers have 

 put the glass in this way. In only 

 one case do we know of any trouble 

 having occurred. Such great advant- 

 ages in economy of material and the 

 lightness of construction are obtained 

 by the use of this wide glass that it 

 is worth making some study of the re- 



R. O. King 



quirements that are necessary for the 

 satisfactory use of 24 inch glass. 

 BUE.iKAGEI FROM HAIL. 



It seems unlikely that 24 inch glass 

 will suffer any more damage from hail 



than 16 inch glass. The reason of this is 

 that glass laid the 24 inch way has more 

 of a chance to spring than glass laid 

 the 16 inch way, so that in case of a 

 sharp blow such as from a hailstone, 



• 24 inch glass, although really weaker, 

 can give way more without breaking 

 than the 16 inch glass, consequently 

 the extra spring makes up for the 

 extra weakness. This action of hail 

 was well illustrated at the Lancaster 

 plant of W. J. Palmer & Son. In July, 

 1905, a hail storm passed over this 

 plant and broke considerable glass. 

 The house with 24 inch glass which 

 had just been built did not suffer any 

 more in proportion than the houses 

 with 16 inch glass. In fact, the great- 

 est damage was done on some 10 inch 

 glass though this was single thick. 

 It seems that a hailstone big enough 

 to break 24 inch glass will be big 

 enough to break 16 inch glass so the 

 danger from hail need not worry any 

 one who wishes to use wide glass. 

 DEAD WEIGHT ON GLASS. 

 Glass is likely to be broken by the 

 dead weight of large accumulations of 

 snow and ice, for this reason it is in- 

 teresting to determine just what 

 weight glass can stand. In Canada 

 where everyone believes we have a 

 great deal of snow, a number of grow- 

 ers are using 20 inch English double 

 diamond. Now English double diamond 

 is about as heavy as American single 

 thick. A box of 50 feet of American 

 single thick glass is supposed to 

 weigh 70 pounds while a box 

 of 100 feet of English double 

 diamond is supposed to weigh 



140 pounds. It follows from this that 

 our Canadian friends are using 20 Inch 

 single thick glass in localities where 

 much more snow may be expected than 

 in localities in the United States. In 

 addition to this, more of the green- 

 house plants in Canada are built on 

 the ridge-and-furrow system so that 

 they get the full benefit of the weight 

 of a sudden snow storm. We have 

 made some tests on the weight of 

 American double thick glass taken the 

 long way and the accompanying table 

 shows the results obtained. 



TABLE I. 



Test of Breaking Strength of 16x24, 



American, Double Thick, A Glass. 



Support, 24 lucbes Apart. 

 Sand Used for Loadiug. 

 WeigLt Load Requirbd Breaking 



of to Break Load per 



Li.ghl. Light. Sq. Foot 



•4 lbs. .-) ozs. 107 lbs. 40.2 lbs. 



4 lbs. 4 ozs. 40 lbs. 15.1 lbs. 



a lbs. 12 ozs. 57 lbs. 21.5 lbs. 



4 lbs. 7 ozs. 61 lbs. 23.0 lbs. 



4 lbs 12 ozs. 110 lbs. 41.3 lbs. 



4 lbs. 4 ozs. 95 lbs. ■ 31.9 lbs. 



The peculiar point about these 

 results is that the strength does 

 not depend at all on the thick- 

 ness You will notice that one 

 light of almost the same thickness as 

 the light which took 110 lbs. to break 

 broke at only 40 pounds. Another 

 peculiar feature you will notice is 

 that although the glass is supposed to 

 be double thick and each light should 

 therefore weigh four pounds 11 1-2 oz. 

 in order to make 90 pounds to a box 

 of 19 lights, there is not one light up 

 to weight. You will probably find that 

 this is the general case and although 

 you pay for double thick glass you 

 really get what ought to be called 

 single thick. The glass taken for our 

 test was selected at random and the 

 weights found therein are confirmed 

 by some weights taken a short time 

 ago in Philadelphia. Selecting two 

 boxes at random each light was 

 weighed carefully and in one box 14 

 lights out of the 19 weighed less than 

 four pounds each In the other 13 

 lights out of 19 weighed less than four 

 pounds each and some of them were 

 very much less than four pounds each. 

 Leaving out of consideration two or 

 three extra heavy lights in each box 

 the remainder of the glass was prac- 

 tically single thick. This probably 

 explains why Canadian growers find 

 English double diamond really as 

 strong as American double thick. In 

 order to cover this point the weight of 

 six boxes from two different factories 

 is given herewith. 



The glass is all labeled A. double 

 thick and is as fine looking glass as 



