Two More e-Slipsticks

The GIMP is treating me better these days. I'm over the hump of the learning curve; virtualizing a slide rule is no longer a multi-hour exercise in frustration. By the last SR, I even figured out how to force my scanner to use a neutral color balance, instead of the default of "fluorescent." (Hint: print out a few of these on a B&W laser printer, and put them adjacent to the SR.)

Two more rules for today (and probably no more for a little while, as I'm out of good SRs.)

N904-T Decimal Keeper
One of the pitfalls of the slide rule is that it has no concept of decimal places. Multiplying 2 x 3 will give 6, but multiplying 200 x 300 will also give 6. It's up to the operator to determine how many zeros should be stuck at the end (or the beginning) of the result.

This SR has an extra set of scales for finding the decimal place. In addition to the regular C and D scales that go from 1 to 10, the back of the rule has C* and D* scales go from 10^-10 to 10¹⁰. You can use these scales to get a crude result that gives you decimal places, then go back to the regular scales and calculate a more precise result.

Decimal finding scales and gadgets (good overview here) never really caught on. I think the main reason is that it's fairly easy to mentally estimate whereabouts the result will be.

Like every other SR I have, I picked this up at eBay. This SR was NIB NOS, or New In Box New Old Stock. It was stock that had never been sold. There's lots of that with SRs. The arrival of the calculator wiped out the slide rule industry overnight -- nobody saw it coming. There were entire warehouses of the things that were never sold. Even today, people are discovering troves of unsold SRs.

140-ES Microline
This is a small plastic rule that Pickett produced near the end of the slide rule era. It's one-sided, which makes it a simplex.

REFERENCE: Previous virtual slide rules. Maybe I'll rescan them some day to improve the color.
N525-ES StatRule
N4-ES Vector-Type LOG LOG
N600-ES Log Log Pocket Rule

UPDATES: One more rule: the N3-T Power Log (visually, it's the best quality scan so far, IMHO. Now that I finally got one real good scan, I am at peace... for the time being.) I've also added an embryonic gallery page of these rules, and an example-based "howto guide" on basic slide rule calculations.