Need Grubb Lens Expertise

[pgk]

Do we know that the serial numbers are sequential?

The ledger show what appears to be the completion date of each lens. So we know 1559 (the serial number at which the ledger starts) was completed on 7th December 1863 and the last recorded lens is 3733 which was finished on 14th January 1877. So yes, certainly sequental. There are later 'anomalies' in that some Petzvals (oddly enough sold as projection lenses for a Triunial Lanter) were sold much later under Sir Howard Grubb's name in the 1890s and it is possible that they were old lenses which were finalised much later as they have much later serial numbers and the lantern has a mix of previously finished, early and later lenses! But the ledger is clear enough.

FWIW Willeica and myself conjectured at length over the serial numbers and the first series of lenses appear to end in the early 4000s, then a second, much smaller set of lenses have serial numbers in the very low 5000s. It looks as though in between records may have been lost and a new sequence initiated, but this remains conjecture and if serial numbers in the high 4000s turn up it will be wrong. Given the very low numbers of lenses bactch built (sometimes even single lenses were made, I'd suggest that yours was built to order. The fact that the adverts list a C1 as a rigid lens (like yours) suggests that options were available. FWIW the brasswork of Grubb lenses seems to have been slightly variable and threads aren't always interchangeable although they were evidently meant to be. So handmade and a customer's requirements could have easily been catered for as a result.

I suspect that very few of the larger lenses were ever made. One of the reasons may well be that obtaining good quality glass in larger sizes was difficult - this was especially true for the even larger telescope objectives.

[Willeica]

The camera lens business was originally done at Charlemont Works just on the South side of Charlemont Bridge and the eldest son of Thomas, called Henry Thomas Grubb, was involved. When the larger Rathmines Works were opened in the 1860s in order to make the Great Melbourne telescope the work was all centralised there. I believe that Thomas felt that his youngest son Howard was the brightest and the best and he pulled him out of his engineering studies in Trinity College to work on the Melbourne Telescope and he eventually took over the complete management of the firm. It seems that Henry Thomas went into the Bank of Ireland to succeed his father and he passed away in 1902 in far less prosperous circumstances than his younger brother. As for the lists we have seen, there are far too many for each date for these to have the output of a single day. I believe that the record book just shows lenses being completed or more likely being taken into inventory. it is a pity that we don't have the complete book here in Dublin as we could do a lot better analysis here than someone based in the North of England who does not know Dublin at all. My view is that some of the lenses may have been started in Charlemont and then finished much later in Rathmines. Also some may have been done in slack periods and finished later. I am very familiar with Leica serial numbers and they show a lot more chronological overlap than some people might think. I am sure that Grubb was no different and often produced batches of a particular type with a number series which would lead to some overlap, particularly if he allocated other number series to different lens types. Looking at his Petzval and Aplanatic outputs that certainly seems to have been the case.