p. 4

1113
-1274-

1867.

Milwaukee March 9th, 1867.

P.S. Chase, Esq.
Philadelphia Pa.

Dear Sir,--

I have to return my thanks for several valuable and interesting brochures. Do you investigate the annual as well as daily wave of barometrical pressure? Six years of observations I have made here have been reduced to 32 degrees temperature and the monthly means found by officers of the U.S. Lake survey as follows:

Jan. 29, .385
Feb. 4, .368
March 29, .307
April 29, .334
May [18?], .300
June [29], .356
July, .356
Aug, .352
Sept, .386
Oct, .372
Nov, .338
Dec, .403

Means. .355

Projecting a curve with these figures and drawing a line through the middle of the slopes, to represent the earth's orbit you will find a tide with 4 max. and 4 min. corresponding with the cardinal points of the ellipse: This can hardly be accidental, but I have not the mathematics nor the time to study the cause and so must refer it to you. Perhaps a new mine of truth may be discovered on this lead:*** (Sketch No. 67).

Very truly yours,

I.A. Lapham.

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Dr. I.A. Lapham,

Dear Sir,--

I thank you for your letter of the 9th and its suggestive enclosure. I am obliged to be absent from the meeting of the