Persian Gulf Collection

Persian Gulf, an arm of the Indian Ocean, lying between Arabia and Persia. Its length is 600 miles, its breadth varying from 50 to 250 miles. The total area is about 75,000 square miles. The order of its periodic currents is precisely the reverse of those of the Red Sea, as they ascend from May to October and descend from October to May. The greatest depth does not exceed 50 fathoms. Oriental geographers give this gulf the name of the Green Sea, from the strip of water of a greenish color lying along the Arabian coast.

References:

The New Student's Reference Work (1914) pg. 1456