The RHS needs your help.
The first one looks to me like a thyme machine… 
But seriously, knowing that this is the Royal Horticultural Society, I would think that was an early or old experimental type of grinder that is missing a few pieces. Or a device that measured, cut, stripped or did other things to fruit and other vegetables. More pictures are needed, and from different points of view.
Maybe an early version of this? 
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Warning: do not search for “old spice stripper” in google if you are at work…
I don’t know what it is – I’d have to have a close look at it, I think – but the second picture doesn’t show a “clamp”. There is a two-position switch at the bottom that, I am pretty certain, engages or disengages a magnet (you can see it below where it says “clamp”) that holds the apparatus down onto a steel table-top, like an optical table. That is, moving the switch causes the thing to “clamp down” toightly and almost immovably on an appropriate table. There are three legs with levelling screws on them so tat you can be sure the thing is level.
Exactly what it does, I don’t know. It looks as if it might be a mount for some kind of equipment. The two knurled knobs look suspiciously like the points where you attach electrical wires. The black cylindrical body might be a battery or a motor or something.
This ought not to be hard to identify. It’s got a legible label on it – Cambridge Scientific Instrument Co. Ltd. , and it appears to be item # 10463. A quick look onthe internet confirms that there are lots of copies of their catalog out there for sale and in libraries.
Mirror galvanometer? Cf.
http://www.mhs.ox.ac.uk/wp-content/themes/mhs-2017-responsive/imu-media.php?irn=39789
Sure looks like it to me.
Hmmmm. yes.
I’m thinking the RHS aren’t trying very hard.
The first one looks like you add things to the two cylinders by taking the tops off the two tubes to the far right and left. I suppose you would set the crank beforehand so that the toothed racks would be even in height. Turning the crank left or right would seem to force the contents up into the bowl. The large tubes likely have pistons in them.
Turning the crank may also spin the round table?
It would be nice to see the underside. It seems there is a valve between the two cylinders. A mixing/pressure control?
Maybe it demonstrated some aspect of how different things flowed/mixed? Displayed upon the rotating table?