I believe it is very difficult to make any recommendations or give any advice for site survey expeditions except of a very general nature. When you start out anew, then, as Dr. Scorer has already stressed very strongly, the first thing you have to do is to contact the meteorological office or the local meteorologist. There is no need to go into detail for I think you all realize that the statistics presented by the weather bureau do not serve our purpose. They are made for a different purpose than ours, and you will always have to go back to the original records and pull out from them the data that may be useful. Suppose you have done this, and you have located either on a world-wide scale the country that is the most promising, or within the country the most promising place as far as cloudiness is concerned. Then what are the next steps ?

In 1957 the Joint Observatory of Yale and Columbia Universities commenced a series of site surveys in Australia under the direction of Dr. I. Epstein. While astronomers at Mount Stromlo Observatory were greatly interested in this activity, it was not until 1958 that Mount Stromlo actively commenced site testing. Tests were initiated in the first instance with a desire to find a not-too-distant location suitable for a field station where observing conditions would be better than those at Mount Stromlo, and later with the idea of finding a site anywhere in Australia which would satisfy the needs of a large telescope.

Wilson. — I would like to discuss briefly a site survey as an optimalization problem.

Wilson. — In the report of the working-group of Sub-Commission 9 b, several recommendations are made. On page 23 of their report the working group recommends that :

1. scales be specified for the various quantities to be measured;

2. equipment suitable for field work be developed and construction standards for this equipment be specified;

3. scales be correlated whenever one and the same quantity may be measured by different methods,

and finally, the recommendation was made that a Symposium be held, in order to discuss and act on these recommendations.

It is a great honour and pleasure for me to welcome, at the opening of the last session of this Symposium, the presence among us of Prof. Oort, Retiring President of I. A. U. I would like to thank him for his interest in the problems we are dealing with, and I am confident that our discussions to day will enable him to tell the Executive Committee of the Union that we have usefully spent our time here.