Sentence:  The photochemical reaction cells consisted of 10 mm. i.d. Pyrex tubing , 5.5 cm. <WSD>long</WSD> , diffraction effects being minimized by the fact that the light passed through only liquid glass interfaces and not gas glass interfaces . 
Meaning of the word marked with <WSD> tags:  primarily spatial sense; of relatively great or greater than average spatial extension or extension as specified