Boulton was not, however, exclusively engrossed by engine affairs. Among other things he informed Watt that he had put his little boy Jamie to a good school, and that he was very much occupied, as usual, in entertaining visitors. “The Empress of Russia,” he wrote, “is now at my house, and a charming woman she is.” The Empress afterwards sent Boulton her portrait, and it was long one of the ornaments of Soho. Amidst his various occupations he contrived to find leisure for experiments on minerals, having received from a correspondent in Wales a large assortment of iron-ores to assay. He was also trying experiments on the model engine, the results of which were duly communicated to his partner.[144] [143] Boulton to Watt, 24th February, 1776. Boulton MSS. [144] Watt was himself occupied, during his temporary residence at Broseley, in devising improvements in the details of his engine. Boulton says--“I observe you are thinking of making an inverted cylinder. Pray how are you to counterbalance the descent of the piston and pump rods, which will be a vast weight? If by a counterweight you gain nothing. But if you can employ the power that arises from the descent of that vast weight to strain a spring that will repay its debts--if by it you can compress air in an iron cylinder which in its return will contribute to overcome the _vis inertiæ_ of the column of water to be raised, you will thereby get rid of that unmechanical tax, and very much improve the reciprocating engine.”--Boulton to Watt, 24th February, 1776. Boulton MSS.