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40 without breaking than that of any other wood with a similar specific gravity. Like that. of second-growth hickory and ash, the wood of young trees is most-esteemed as the fiber is stronger and more elastic. The best wood is said to be derived from trees between 40 and 60 years of age. At present the bulk of the logs com- ing into the market are from trees several hundred years old and from 3 to 5 feet in diameter. The wood splits with difficulty, although | it works well and can be sliced into veneer to 1/80-inch in thickness. Wood is Durable There is an aromatic oil in Spanish cedar which is said to repel insects and render it immune to wood-de- stroying fungi. The wood is durable under pfactically all conditions and has been reported to be proof against the attacks of white ants which are THE LOGS ARE FLOATED TO THE PORT OF SHIPMENT IN LARGE RAFTS. THIS IS SHOWN IN THE UPPER THE Sa MARINE REVIEW Develop Light Aggregate January, 19j9 4 Spanish cedar is employed for a great variety of special purposes for which it is always in the highest demang It is regarded as the most usefy| wood in tropical America. The wood is often curiously figured and is cap. able of taking a good polish, For these reasons it iS sometimes yseq by the cabinet maker. for Concrete Ships Investigations conducted under the auspices of the International Con- crete Ship association, New York, have resulted in the development of a new form of aggregate whose use makes it possible to produce con- crete ships which weigh only about two-thirds as much as formerly but whose structural strength is three times as great. These results were achieved by using cement clinker, ~ THE LEFT VIEW. THE ILLUSTRATION AT SHOWS HOW MAN POWER IS UTILIZED IN LOADING LOGS FOR TRANSPORTATION TO THE RIVER. AFTER THE TREES ARE FELLED THE LOGS ARE SQUARED, THE MARKS OF THE ADZE ARE PLAINLY SEEN IN THE VIEW AT THE RIGHT so destructive to woods in the tropics. There are, however, no authoritative records showing that it is entirely immune to the ravages of these in- sects or to the toredo. All users of cedar and writers on timber seem to agree that the wood is durable when in contact with the soil and that it resists the action of the weather. The quality of withstanding the action of the elements is due prob- ably to the presence of an oil in the wood, Spanish cedar is not generally rated as a shipbuilding wood, although in tropical America it is highly esteemed for building small boats. Consider- ing its lightness in weight and great durability in contact with water, it is difficult to understand why Span- ish cedar has not been requisitioned more extensively in the past for boat building in the United States, It is of interest, however, to note that it has recently gained recognition in this country as a boatbuilding material, when more than 100,000 feet have been sold to one Organization for making lifeboats. In the opinion of those who know Spanish cedar hest there is no better wood extant for this purpose,, and it is believed that after its good. qualities become more generally known the better grades of logs coming into this country will be requisitioned for boat construc- tion. : Closely Related to Mahogany Most architects and wood users in this country do not know that Spanish cedar is not a cedar at all; they think of it as a soft wood or conifer. This is a mistake. The true Spanish cedar is a 'broad-leaved tree and is closely allied to the mahogany which was at one time considered the king of shipbuilding woods. Span- ish cedar 'closely resembles mahog- any in many important respects only it is lighter in weight, which is a quality much in its favor for so im- Dortant a use as boat building. Next to mahogany the cedar is the most valuable of all the tropical American trees. If the mahogany be regarded as the king of the forest, the cedar may easily claim supremacy as the queen. While mahogany is pre- eminently useful for fine furniture and interior trim, and for all purposes Tequiring great beauty and durability, which can be obtained at any cement plant, in proportions of three of clink- er to one of cement. The mixture after pouring, weighed 105 pounds per cubic foot and in a compressive test conducted seven days after pour- ing, broke at a pressure of 4863 pounds per square inch. In 28 days it broke at 9240 pounds. A density test showed 2.5 per cent moisture. In making this concrete, the cement was ground to a fineness of 97 per cent through a 200-mesh sieve before calcining, and after calcining it was ground to a fineness of 95 per cent through 200 mesh. This cement was aged 60 days in the clinker and was used comparatively freshly ground The aggregate was composed of hard- burned clinker, fresh from calcining, crushed and ground to take up the voids, and ranging from %-inch to a fineness of 200 mesh. The concrete was mixed with 12 per cent water and was tamped hard. When using this mixture in a cement gun, 8 to 10 per cent of water may be used. In order to produce still better re- sults, the association recommends that after fine grinding, the agegre- gate be moistened and molded into uniform | briquettes and dried in an GCven prior to calcining, as this meth- od results in its expansion to 10