138 MISCELLANEOUS FARM SUBJECTS 



to be the most desirable thickness for common sizes of silos under 

 existing practice. 



Only a first-class Portland cement which has been stored in a 

 perfectly dry place should be used. The proportions of cement and 

 gravel will vary with different grades of gravel. If broken stone is 

 available and cheap, it may be used with sand instead of gravel. 

 To obtain the best grade of concrete the gravel and sand must be 

 clean and durable and the cement must be in such a proportion as 

 to nearly if not altogether fill the voids or open spaces between the 

 sand and gravel. To obtain the strongest concrete with the mini- 

 mum of cement the sizes of the gravel should be in the right pro- 

 portion and vary from the largest to the smallest sand particles. 



Gurler Silo. One of the most successful types of silos is that 

 generally known as the plastered or Gurler silo. This type is espe- 

 cially adapted where there is still a local supply of native lumber 

 which furnishes a cheap building material. The Gurler silo is built 

 much like a frame house, except that it is round in form, with a 

 lining of boards running lengthwise around it, somewhat like the 

 hoops of a barrel which give it strength to resist the immense pres- 

 sure of the silage. Its cement plastered wall protects the wood 

 framework from decay. Some of the strong points in favor of this 

 style of silo are: (1) Can be built entirely from ordinary lumber; 

 (2) requires no highly skilled labor for its construction; (3) pre- 

 serves the silage as well as any type of silo in use; (4) is strong and 

 durable when properly made. 



Ventilation. -Carbon dioxide, a gas heavier than air, will col- 

 lect above fresh silage if not given an opportunity to flow away to 

 a lower point. This might be the case where the doors are not 

 continuous and the gas is pocketed below a door. Care should be 

 used in beginning work in a silo after it has been standing for a 

 time partly filled with fresh silage. If silage is allowed to fall into 

 the silo for a time, the carbon dioxide will be stirred up to such an 

 extent that there will be no danger from asphyxiation. Although 

 many silos are provided with ventilators, it is doubtful if they are of 

 any practical value whatever. Under usual conditions, it is best to 

 prevent circulation of air above the silage. 



It is desirable to prevent the freezing of silage in the silo dur- 

 ing cold weather as far as possible and the silo of a construction to 

 prevent freezing to the largest degree is the preferable one, other 

 things being equal. It is difficult to make a comparison between 

 the merits of the various types of silos in this respect owing to the 

 inability to find them under like conditions. Freezing of silage is 

 due to loss of heat; first, through the silo wall; and second, to the 

 air in contact with the feeding surface. The first loss may be re- 

 duced by using a non-conducting wall in the silo and the second by 

 preventing the circulation of air above the silage in the silo. 



It may be impartially said that, as far as the prevention of 

 freezing of silage is concerned, the stave, stone, single wall brick 

 and concrete silos are of about equal merit. Any kind of an air 

 space will partially prevent freezing, depending upon how little the 



