32 



HORTICULTURE 



July 4, 1914 



This simple little Chinese puzzle has to ilo 

 ivith the load of the roof exerted on the 

 rafter at a certain point. 



How We Make Sure 



Our Roofs Are Safe and 



Nn this is not a kite, but a 

 (liagram of the tspers the 

 wind ruts up when it starts 

 (Hishing^ on the roof. 



h 



Sure 





IT'S easy enough to say that if a piece of iron, of a 

 certain size and strength, will support a load of 

 so many pounds, that one twice the size, would 

 support twice the load. That's good enough as far 

 as it goes — but it doesn't go far enough when it comes 

 to greenhouse construction. It doesn't, because every 



foot in width that you add to a house, you shift the 

 load. It may increase the load by three, at some 

 points, and decrease it by a half, at others. You ab- 

 solutely must know to a pound — almost to an ounce 

 — just 





(1) How much the weight of the frame itself will be; 



(2) How much the wind pressure will be; 



(3) How much the snow pressure of an estimated given amount will be; 



(4) How and where the pressure will be shifted from one member to another. 



(5) How much margin should be figured in for a "safety factor" or the allowing of a 

 surplus of strength for extraordinary conditions of snow and blow. 



(6) You must know not only the weiglit and pressure exerted on the entire structure, 

 but exactly what the weight and strain will be at any point. 



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These are things that can't be figured out on the back 

 of an envelope "while you wait." 



It takes days, sometimes even weeks, to do it. But 

 we never materially increase the width of our houses 

 or make any radical change in our construction, 

 without first having our engineering department fig- 

 ure out stress and strain diagrams, like these shown 

 here. These particular ones were worked out to 

 prove to ourselves that we could safely build a house 

 83 feet wide and use only two columns. 

 These diagrams proved beyond all doubt that it was 

 a safe and sure proposition: but also showed to us 

 that it was possible to greatly simplify our first con- 

 struction diagram, making the house more desirable 



in every way and reducing its cost considerable. 

 It took our engineering department over two weeks, 

 working steadily, to reach these conclusions. How 

 then, any ordinary mechanical draughtsman can be 

 depended on to fi(iiiir safe on the engineering prob- 

 lems involved in big greenhouse building, is more 

 than we can understand. Or how even a skilled engi- 

 neer can handle it without the aid of information 

 and data, only such as can possibly be found in the 

 possession of a greenhouse concern of years and years 

 of experience like Lord & Burnham. 

 When you want to build a safe and sure house, be it 

 big or little, let's talk it over together. Say when 

 and where and we'll be there. 



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TorC fe^tVurnhamfi. 



^S SALES OFFICES : 



H NEW YORK BOSTON PHILADELPHIA CHICAGO ROCHESTER CLEVELAND 



^^ 42nd Street Bldg. Tremont Bldg. Franklin Bank Bld«. Rookery BIdg. Granite Bldij. Swetland R\Aa 



» TORONTO. CANADA. 12 Queen S»., E. FAOrORIES: Irvingtotv N. Y. De. Plalne.. III. 



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