I think you've got a good idea going. I only have a few nit picky things to say, mostly about clarifying and expanding ideas.
tabbed Isaac walked groggily into the lab, which he had only abandoned a few hours prior.
Did he abandon the lab or simply leave it? If he abandoned it then why did he return at all? Plus, why was he groggy? Was the hour late? Early? He just woke up?
tabbed The leather-bound briefcase and thick wool jacket made a thud and thwump as they were placed on a desk in the corner of the room. Isaac rubbed his eyes and turned to the cages that lined the wall containing rats in different degrees of health. "Good," he thought, "they managed to get me new specimens already this morning. I'll have to thank Dianne when she brings my lunch."
Did the jacket bounce when it hit the table? That's the only reason I can think of that it would make two sounds upon landing. Unless there's some other reason you haven't stated. I'd also like to know what he's working on and why the rats are necessary.
I like the idea of a steampunk computer. I thought the sounds the keys made was a nice touch. At first I thought the contraption on the table was a separate device. After a second read through I figured out that it's the same device. I'm still getting over a cold so my brain isn't as quick as it usually is, so the fault for that misunderstanding is probably mine. In the last paragraph I assume that this message system takes longer than a hand-written letter. A little clarification there would be nice.
That's all I have to say. Keep writing!