162 REFRIGERATION AND REFRIGERATOR INSULATION ON BOARD SHIP. 
ber seeing one machine, which had been taken apart after nine months of service, twelve 
hours a day, and the oil was perfectly good and put back into the machine when the machine 
was put together again. 
As to the helplessness of an engineer with a hermetically sealed machine, we were much 
afraid of that at first—I know our customers were, and the question was up repeatedly. 
As a matter of fact, we started with spares in the first marine installation we made—we 
had a spare machine in that installation—and we have never since then put on a spare 
machine. 
Mr. R. C. CARPENTER (Communicated) :—Although not a member of your honored 
Society, I am greatly interested in the statements made by Mr. Massa as to the method of 
applying cork insulation for the cold storage rooms of vessels, which is similar to that em- 
ployed in the application of cork insulation in modern cold storage buildings. 
What he states regarding the difficulties with cork is of great interest and points out the 
need for a good insulating material which has structural qualities. 
I have recently made an investigation, rather scientific in its character, respecting the 
heat-insulating properties of cork and an extremely light wood having considerable struc- 
tural strength, which grows in the tropical regions of North and South America and which 
is known popularly as balsa wood or scientifically as Ochroma lagopus. 
I prepared a paper for the American Society of Civil Engineers on the properties of 
balsa wood, which appeared in the proceedings of that Society of May, 1916. In that paper 
I gave results of actual tests of strength and also of heat transmission when employed for the 
purposes of insulation. 
Balsa wood I believe to be peculiarly suited for insulating the cold-storage rooms of a 
vessel, as it can be worked with the same facility as many of our modern woods. It has a 
high insulating value and will in practice, I believe, be found superior to cork. It can easily 
be applied, and, so far as I can ascertain, is not objectionable from any source whatsoever 
when it has been properly treated. If the wood is used in its natural state, it is likely to 
have a very short life, but when treated by the Marr process, its life is indefinitely prolonged 
and its qualities are improved in various other respects. 
Capt. A. P. Lundin, a member of this Society, has had oacde eine experience with 
the use of balsa wood for insulation on shipboard, and with excellent results. There is 
no difficulty of the character mentioned by Mr. Massa as applying to cork, and the insulat- 
ing qualities are superior. The life of the structure is all that can be desired; consequently 
it is only reasonable to expect that, when this material becomes better known, it will be in 
great demand for insulating purposes, 
I investigated the heat transmission Shonen both balsa and cork and present here a 
brief statement of the results which I obtained. 
The heat transmission can be expressed by the following formula :— 
The symbols used are as follows :— 
e = “Specific conductivity,” or heat transmitted per degree of difference of temperature of 
the sides of the material, per unit of time, per inch of thickness. 
