In the September 1990 issue of CJ, we talked in some detail about the use of M-2795 in northern California. More than 100,000 of these insulators were used on two lines during 1900-1901. The top skirt was made of porcelain, with a gutter around the outer edge and an eave spout to direct the water away from the crossarm. The long bottom skirt was made of glass by the Brookfield Glass Co. The two parts were cemented together with sulfur. The glass skirt protected the pin to some degree, but where the line crossed fog prone areas, or during times of rain, the electricity would leak across the surface and cause an arc from the bottom edge of the glass skirt to the pin, which resulted in burning of the wooden pins. The following quote was taken from the August 1901 issue of "The Journal of Electricity Power and Gas":

"On the base of the pin is used a porcelain sleeve 5 inches long, which rests upon the crossarm and projects up beneath the glass petticoat. The object of this porcelain sleeve is to protect the pin in the event of an arc tending to strike from the eave on the insulator to the base of the pin. It also protects the pin from weathering."

Illustration of M-2795 taken from the February 1903 issue of 
"The Journal of Electricity, Power and Gas", which shows 
the porcelain sleeve around the wooden pin.

M-2795 was satisfactory under arid conditions, but the margin of safety was exceeded during wet conditions. The top skirt acted as a flat pan that easily collected dirt. In the 1903 "Journal of AlEE", an article titled, "Bay Counties System", problems with dirt accumulating on M-2795 were described: "The only place where we had trouble with the accumulation of dirt on insulators was near salt water and cement works. Rain is Heaven's own blessing ... it cleans the insulators and stops a good deal of the damage to wooden supports [pins]. This is true of salt water districts especially. The first few drops that fall after a prolonged dry spell causes a good deal of a display which soon passes however and all is quieter and better than it was before." The burning of pins was a constant problem near fog prone areas. Some of the wooden pins were soon changed out with a pin made from steel gas pipe, which had lead threads formed on the tapered end: Another solution was patented by Fred M. Locke. His patent No. 698,976, dated April 29, 1902 (on application filed November 11, 1901), claimed the use of a porcelain sleeve around the pin.

M-2795 showing porcelain sleeve that was suppose to protect 
the wooden pins from being burned by electrical arcing.

M-2795 was fitted with a five-inch porcelain sleeve, that rested on the crossarm and extended up inside the glass bottom skirt. Bill Rohde recently discovered that he has one of these porcelain sleeves in his collection. He did not know what it was until one day we were discussing the problem of M-2795 pins being burned and the use of these simple porcelain sleeves. No other specimens have been reported. Does anyone else have one of these porcelain sleeves? The two photographs of M-2795 with the porcelain sleeve were taken by Bill Rohde. 

Another interesting problem was observed along salt water fog areas, and reported in the 1904 issue of the" Journal of AlEE". In the article titled, "High-Tension Insulators", by V. G. Converse, R. S. Hutton reported the problem with M-2795: "The separate parts of the first ones used, were put together with sulfur, and we had some field fires that we were not able to account for. We afterwards found out that it was due to the fact that the leakage heated the insulator to such an extent that the sulfur was set on fire, and as it dropped down, set the grass on fire around the poles." In March 1904, the insulators in these salt fog prone areas were replaced with M-4384 mounted on iron pins, and the line voltage was increased from 44,000 volts to 55,000 volts. A few specimens of M-4384 have been located in California, and three of them have the #7 -1 marking. It has been reported that some of the M-2795's that were removed from these lines were shipped to Hawaii. Indeed, some specimens have been found there, but I do not know where, or in what service they were used. M-4384 is the largest of the Fred Locke insulators. The fourth skirt is recessed inside the bottom outer skirt much like M-4320, M-4400, M-4415, M-4415A, M4420, and M-4425. 

M-4348 Fred Locke 
14.5 - 9.5 - 9.5 - 6.5 x 12.5

If you would like to learn more about the development of the M-2795 and its use on the two northern California lines, you will have to wait for my new book, which hopefully will be available at the 1994 Houston National. The book will be a rather detailed biography of Fred M. Locke. Much of Chapter 7 has been dedicated to this fascinating insulator. Only two paragraphs from that book have been reproduced here.

Illustration of M-4384 from July 1905 issue of "Electrical Age"

Porcelain Cochrane Bells?