Update to the above:
I have been doing a little research on the inscription and with the help of Omani friends and colleagues; we have a fair translation. Please correct me if I have got the translation totally wrong (I don’t think I have but who knows) 3rd of Dhu AlHijjah 1237 H is 23/08/1822 G.
“On Thursday the 3rd of Dhu AlHijjah 1237 Hijri the scholar father of Nabhan. Jaiid bin Khamis bin Mohammed bin (?) bin Zaid bin Mansour Al Kharoosi Al Abadhi Al Omani has died. Written by his son Khamis”
But why it was inscribed high up on a rock in the dark entrance to a narrow wadi, we are not sure, it could be that this is where he died….?
He was a very famous Omani scholar of the Ibadi religion.
David A Lockwood 
Wadi Bani Kharous Full of Rock Art , and Scripts too , good work ,i have book about rock art but it is in Arabic
Yes a great place for rock-art, spent many hours going over the rocks looking.
I am sure there is still more for me to find.
David.
The top photo looks to be Arabic writing. Have you had it translated yet David?
Dave,
No I have not as yet; it also looks like there is another older inscription underneath.
This and a lot of other rock art is found in what can only be described as a cave of sorts, a large opening at one end and a smaller exit at the other.
The next image was inscribed on a very polished hand hold about half a klick further up the wadi and looks an older version of written Arabic.
David.