Review the attached three files and you'll have a pretty good generic description of how a sight feed or hydrostatic lubricator works. An important feature to remember is that the entire internals of lubricator is under the same pressure, I.E.: boiler pressure, making the oil droplet rise in the sight glass solely due to the weight of the column water in the condenser. Also the "choke" , or orifice in todays jargon, at the inlet of the delivery tube is critical to maintaining that equalized pressure. Yet that choke must be big enough to pass oil to the engine cylinder. In a model it is only .026" diameter + /-. Not mentioned in the description is another choke at the engine steam chest to prevent condensation from backing up into the oil delivery tube. Since the cylinder steam chest is always at a lower pressure than the boiler it is easy to envision the oil droplets rising through the sight glass being pushed through the lubricator delivery tube choke by the boiler steam pressure, through the delivery tube under the boiler jacket, then through the cylinder steam chest choke, and finally into the steam chest cavity where the oil is atomized with the steam down stream from the throttle.
If the three files are too hard to read send me a PM with your Email address and I'll forward them to you.