Sentence:  For very good reasons, the College professors were keen to exclude the new <WSD>regius professors</WSD> - who often received a mere £50 per year from the Crown - from a share in the College revenue, and so men like the chemist Thomas Thomson and the engineer Lewis Gordon (unlike the five older <WSD>regius professors</WSD> of astronomy, church history, civil law, medicine, and anatomy) were without administrative and academic power in the Glasgow institution. 
Meaning of the word marked with <WSD> tags:  A professor who holds a position created by or filled by a royal patron.