This is hard because it's an early plane (little standardization, so different serial numbers of the same type could be quite different), and it's a drawing (no way to know how accurate the artist was, or how much talent for perspective drawing he had).
I'm going to say it's a Short S.41, probably depicting Serial Number 10, which was either the original or the first production S.41. According to J.M. Bruce there were only three of these built -- S/N 10, 20 and 21 -- but it's unclear whether S/N 10 was also the prototype (the "original" that Bruce refers-to in a photo caption) or if "the original" was a separate project that would raise the total number built to four.
The way the main floats are hung and the general shape of the floats in the drawing is consistent with an S.41.
The smaller wing floats in the drawing look to be in about the right mid-wing position for S.41 S/N 10, and would be incorrect for S/N 20 which had it's wing floats located out at the lower wingtips. I think the artist drew them a little too chunky though. Presumeably S/N 21 was rigged generally the same as S/N 20, but I don't have a picture to confirm this (I'm going to assume that it was, though, so the same features that eliminate S/N 20 also eliminate S/N 21).
The tail float in the drawing is a very good match location-wise and shape for the one on S.41 S/N 10. Again, maybe drawn just slightly too large -- perhaps the artist was trying to emphasize the wing and tail floats.
What looks like the leading edge of the vertical stabilizer at first glance is actually a strut anchoring the top of the rudder post to the fuselage. This is a feature of both the Short S.41 and S.42 in it's original seaplane form (circa 1913).
I don't think it's an S.42, though, because the S.42 lower wing is mounted directly to the fuselage, the lower wing tips are distinctly rounded, the S.42 seaplane has no openings in the wing and the S.42 horizontal stabilizer is either narrower or has some taper to it. Also, the S.42 wing floats are tip mounted rather than mid-wing mounted as shown in the drawing. Finally, there appears to have been only one S.42 built, S/N 42, and after July 1913 it was reconfigured and flown as a landplane until it was written off in September, 1914.
The way the upper wing is braced with long sloping struts to the lower ends of the outer interplane struts is also consistent with S.41 S/N 10. The large openings in the wings above and below the cockpit area matches the wing openings of S/N 10, and they disappear on S/N 20 (along with the sloping struts that tie the top and bottom wings together at their ends).
The fuselage seems to have the same number of stations from the cockpit back as S.41 S/N 10, give-or-take one for artistic license. The general shape and layout of the fuselage is also a very good match between the drawing and my picture of S.41 S/N 10.
I'd be more certain if the artist had clearly showed the lower wing completely separate from the fuselage, as it was with the S.41, but it does look like he made some attempt to do this & just didn't do a very good job of detailing the light and shadow effects.
Short S.41 Serial Number 10. That's my story and I'm sticking to it.