THE CUBA REVIEW 25 
Laboratory of Sugar Mill Fertilizer Factory, Comite del Nitrate de Chile, Havana 
advance in this line, is that of the Cuban American Sugar Co., at two of its mills, ‘“Tin- 
guaro” and “Constancia.’”’ Mr. Caldwell, the manager of Tinguaro, has for many 
years had connected with his agricultural department a research laboratory in which 
analyses have been made of soils, fertilizers, etc., and the chemist in charge of this work 
has also had charge of experiment work with fertilizers in the lands from which the cane 
supply of ‘““Tinguaro” is obtained. This company operates over a very large area con- 
taining many different classes of soils, so that many different experiments were required 
in order to ascertain the class of fertilizer best adapted to each of the varieties of soil. 
In the same way at ‘‘Constancia” investigation work has been carried on for a number 
of years, the results obtained now being sufficient to standardize pretty accurately 
the requirements of each of the soils from which her cane supply is obtained. Other 
mixing plants of a similar capacity have been established at Centrals ‘Mercedes,’ 
“Cuba,” etc., etc., some of these plants having attained a production as great as 8,000 
tons per year. Some of them supply the needs of their own cane growers, and also sell 
a part of their product to growers not immediately connected with the estate. Among 
