Jan u All Y 31, 1907. 



The Wc^y Florists^ Review, 



785 



quantity of material is to use the ridge 

 and furrow system, making the pitch of 

 the roof as low as possible and using as 

 wide glass as you will risk. Remember- 

 ing that we are meeting the condition of 

 no sunshine, it also follows that it does 

 not matter whether the houses run north 

 and south or east and west. Finally, 

 provided your houses are built to meet 

 that worst of conditions, no sunshine, 

 will they not then take care of them- 

 selves under better conditions; that is, 

 with sunshine? 



The Widest Span to Date. 



It may be interesting to describe the 

 process of designing a new type of 

 greenhouse for which practically no data 

 is furnished by previous actual building 

 experiences. A design for an even-span 

 house 150 feet wide and having only 

 five rows of supporting posts has recently 

 been completed. This house is a great 

 departure from present standards and 

 will set a record for wide houses which 

 is not likely to be surpassed for some 

 time, or at least until we can profit from 

 the success or failure of the gentlemen 

 who are willing to experiment on such a 

 grand scale. 



Beginning with the glass, it is desired 

 to lay it with the suporting bars twenty- 

 four inches apart. Referring to the table 

 before stated, it is found that the aver- 



per foot. Adding two and one-half 

 pounds per square foot to cover the 

 weight of the glass and bars we have ten 

 pounds per square foot as the total 

 working load for the truss. Supposing 

 the posts are spaced eight feet four 

 inches apart lengthwise of the house, then 

 each truss has to carry a total working 

 load of 2,333 pounds. 



This loading may be considered as be- 

 ing distributed at the joints and the ends 

 of the truss. The stress or strains pro- 

 duced in the members of the truss can 

 now be determined by means of the de- 

 vice known as the stress or strain dia- 

 gram. After finding in this way the 

 strain in each member of the truss, cal- 

 culations must be made to obtain the 

 correct size for each. For instance, if 

 the sash bar is of cypress, then it must 

 be heavy enough to stand a working end 

 strain of the 3,200 pounds. In the case 

 under discussion it has been calculated 

 that this bar must be l%x2K', this size 

 giving a working end strain of 3,200 

 pounds and a breaking strain of 12,800 

 pounds. The lower member, which must 

 carry 3,000 pounds, is in tension, so 

 should be of iron or steel and by a sepa- 

 rate calculation it is found that %-inch 

 diameter is suitable for this strain. The 

 other members of the truss are propor- 

 tioned in the same way. 



Having now designed the truss to carry 



OILED CLOTH FOR PROTECTION, 



Will you please give me directions for 

 preparing cotton cloth, with boiled oil 

 and rosin, for covering frames? It is so 

 warm here, Miami, Fla., that we do not 

 need glass protection, but build our 

 houses with lattice for protection against, 

 wind storms. I think the oiled cloth 

 will keep out tlie too hot rays of the 

 sun. J. W. W. 



I can see no reason why cloth could 

 not be used to advantage for this pur- 

 pose, particularly as far south as Miami,. 

 Fla. Would suggest raw, rather thani 

 boiled oil, as the latter stains the cloth 

 and thus impedes the light. As light ia 

 so essential to plant life, it is impor- 

 tant such covering be made as transpar- 

 ent as possible. The following furmula 

 is generally used in preparing cloth for 

 this purpose: Six pints of raw oil, two 

 ounces of sugar of lead, eight ounces of 

 white rosin. This preparation is applie<l 

 hot with a brush and for this reason 

 should be prepared in a kettle or other 

 receptacle that will withstand heat. 



Sugar of lead does not mix readily and 

 I would use only enough oil at first to 

 cover it. Agitate with a stick or grind 

 with a pestle until the emulsion is per- 

 fect, then add the balance of the oil and 

 rosin. Stir well on a slow fire until all 

 the ingredients are incorporated. 



Truss Roofed House 150 Feet Wide to be Built by the King Construction Co. 



age weight required to break the glass is 

 thirty pounds per square foot. This is 

 equivalent to about one foot of wet snow. 

 The glass is hardly likely to be called 

 upon to stand more than this, so the 

 question of strength against dead weight 

 can be considered settled. 



The framework of the house must now 

 be made strong enough to carry some- 

 what more weight than the glass could 

 stand, so that the glass would break be- 

 fore the framework collapsed. Consider- 

 ing the length of rafter, it is seen to 

 divide conveniently into three lengths of 

 twenty-eight feet each, on each side of 

 the ridge. As it is desired to use as few 

 posts as possible, suppose it is decided 

 to put in a post at every twenty-eight 

 feet section and carry the intervening 

 space by truss work of the form shown 

 in the sketch reproduced herewith. The 

 load that each truss is to carry, in order 

 to be strong enough to support the glass 

 under its breaking load, is found by tak- 

 ing the area of roof supported by this 

 truss and multiplying this by the weight 

 per square foot that the glass will bear; 

 that is, thirty pounds. Now, this is the 

 breaking load of the glass that the truss 

 would be called on to bear, but it would 

 be safe to take the working load as one- 

 fourth of this, or seven and one-half 

 pounds per foot. This even would be a 

 high working weight, as ordinarily the 

 truss has only to carry the weight of 

 the glass, which is less than two pounds 



the roof it is necessary to design the 

 posts or columns to carry the truss. The 

 strength of a column depends greatly on 

 its length, so by properly bracing a long 

 slender column it is practically divided 

 by the bracing into a corresponding 

 number of short columns. In the wide 

 house under consideration it is found 

 that 2-inch pipe properly braced in every 

 direction will carry the roof. 



The design is now complete, leaving 

 the glass the weakest member, as it 

 should be, for it is seen that although 

 the breaking strength of the glass is 

 thirty pounds per square foot, and the 

 breaking strength of the truss work is 

 the same, yet the glass is not uniform in 

 strength, whereas the trusses are, and as 

 thirty pounds is an average, it follows 

 that half the glass would be broken by 

 the time this load would be reached and 

 if half the glass is broken, half the 

 weight has gone with it, so our f rams- 

 work stands to be subjected in the limit 

 to only one-half of its breaking load. 



There is a good deal of theory about 

 all of this, but many of those here now 

 will likely be at the S. A. F. convention 

 at Philadelphia in August and there will 

 then be an opportunity to see how it 

 has all worked out. 



Cloth thus treated in a short time 

 becomes hard and in a year or so very 

 brittle, being easily torn. It is not im- 

 probable that this formula could be im- 

 proved upon by adding paraffin or bees- 

 wax to increase or prolong pliability. 

 A little experimenting often proves goo<l 

 and one season's use would demonstrate 

 the best formula. Elmer D. Smith. 



AUGUST.\, Ga. — Public sentiment here 

 is growing in favor of clearing the trees 

 of mistletoe, as it is claimed it threatens 

 the life of the trees. 



DOBBS FERRY, N.Y. 



The regular meeting of the Dobbs 

 Ferry Horticultural Association was held 

 in Odd Fellows' hall Saturday evening, 

 January 26, Vice-President Robert Bore- 

 ham in the chair. There was a prize for 

 the best pot plant in not larger than a 

 6-inch pot, which was awarded to J. 

 Bradley, gardener to H. Sedenberg, for a 

 cyclamen. H. Kastberg, gardener to Miss 

 Masters, was second with a cineraria. 

 H. Keiling, gardener to Mr. McComb, 

 staged some roses which were remarkable 

 after the bad season we have had. 

 Among them were La France, Bride, 

 Bridesmaid, Golden Gate, Perle and 

 Ivory. There is a prize for the best ex- 

 hibit of any kind to be competed for at 

 the next regular meeting. J. Bradley 

 will give a short talk on the growing of 

 evclamens. 



Windsor, Ont. — C. R. Tuson has pur- 

 chased the building now occupied by 

 his business. 



