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THE GARDENERS' MONTHLY 



[March, 



ular descent throughout the entire length of from 

 six to ten inches in one hundred feet. 



There is then no need of expansion tanks in 

 any other part of the arrangement. 



Where the position of the boiler or the construc- 

 tion of the buildings will not admit of such an ar- 

 rangement, take the shortest practicable line to the 

 highest point accessible, and make the expansion 

 tank there. I am not prepared to say what the 

 elevation of the tank should be, but believe that 

 for large boilers it should be at least ten feet. 



Heat is the disturbing influence that starts and 

 keeps the water in motion. The rapidity of circu- 

 lation (upon which depends the heating capacity 

 of the water), is governed by the amount of pres- 

 sure upon it and the intensity of the heat in the 

 furnace. Therefore it is necessary to have the ex- 

 pansion tank elevated considerably above the 

 pipes so that there will be a head of water exert- 

 ing a continual pressure on every part. A dis- 

 placement of water in any point is then quickly 

 felt throughout the whole system. 



A gradual descent of pipe all the way around, 

 with as few bends and turns as possible is the sim- 

 plest plan that can be adopted, and will give the 

 most perfect and economical results ; however it is 

 possible to make an endless variety of digressions 

 from this rule, and still keep up a circulation 

 which will be more or less retarded by every varia- 

 tion from the direct course. 



A pipe may vary from a straight line in any 

 way, provided there is a vent-hole for the escape 

 of air at every point where it changes from ascend- 

 ing to descending grade. It may have a grade of 

 ten inches in ten feet, or drop perpendicularly for 

 several feet, and then fall only a very few inches 

 in the next hundred feet, if necessary, but all such 

 irregularities should be avoided as far as possible. 



It is a matter of the first importance that there 

 shall be no elevated points in which air can accu- 

 mulate, because water will not circulate freely 

 through pipes which contain air chambers. 



There is always a considerable quantity of air in 

 water, some of which is expelled by heating. This 

 may be observed by standing a tumbler of water 

 in a warm place. In a short time small bubbles 

 of air will be seen on the inside of the glass which 

 gradually rise to the surface of the water and dis- 

 appear. 



The air which is liberated from the water in a 

 boiler or its connections rises to the highest part 

 and flows on top of the water as long as it 

 can ascend, but it will not flow down hill. If 

 there is an opening at the highest accessible point 



the air will escape, if not, it remains there occu- 

 pying space which should be filled with water. 



Sometimes heaters which worked very well at 

 one time become deranged by the settling of a 

 pier or other disturbing cause, making a depression 

 in a pipe at one spot, thus forming a barrier to the 

 flow of air which wholly or partially checks the 

 circulation of water. 



The remedy for such a defect is to straighten 

 the pipe so that the air can rise to some higher 

 point of escape or else drill it at the summit of 

 each undulation, and insert a stop-cock or other 

 arrangement which can be opened occasionally or 

 constantly for the escape of air. 



There is, however, no necessity for vent-hole or 

 other opening throughout the whole system of 

 pipes if the expansion tank is at the highest point, 

 and all the pipes descend from it through their en- 

 tire circuit. In such an arrangement the air which 

 is liberated in any point can always ascend, and 

 will find its way up to the tank and escape there. 



NEW OR RARE PLANTS. 



New Double Bouvardias. — Messrs. Nanz & 

 Neuner send us flowers of two double scarlet bou- 

 vardias, one more double than the other, which 

 seem to be of the leiantha class. They are there- 

 fore very distinct from those heretofore raised, and 

 will probably add a new item of interest to these 

 very popular winter blooming flowers. 



DiEFFENBACHiA AMCENA. — This is one of the 

 Arum-like family, now becoming so popular among 

 leaf plants. It is thus described by Mr. W. Bull, 

 the introducer: "An effective variety of this 

 showy race of Arads, obtained from the tropical 

 regions of South America. Its oblong acute leaves 

 are of a deep green, marked with very abundant 

 elongate blotches of white and pale yellow, which 

 are as well defined on the under as on the upper 

 surface. It is a very attractive plant, on account 

 of its bright and abundant maculation." (See cut 



page -JT.) 



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SCRAPS AND QUERIES. 



Steam Heating. — We shall have an illustrated 

 article in our next by Mr. C. F. Evans, of Phila- 

 delphia, on " Steam Heating," which will explain 

 very clearly much that mere letter press will not. 



Growing Carnations.— The following letter 

 to a distinguished botanist has been handed to us 

 with the suggestion that the writer would perhaps 



